chore: release Anvil 0.4.0, Lathe/Temper/Knurl 0.3.0, Planish/Braze/Ballast/Forge 0.2.0, Crucible/Weld 0.4.0

The producer-feedback round: stable note tracking, the NOTE pitch source with Key lock and Follow bends, unsure-means-neutral fallbacks, Anvil's Enhance mode, MAIN and ADVANCED pages, Ballast on Grid by default, and Crucible's sure-note slice names with a song key. Adds docs/pitch.md for the shared pitch source, updates every changed plugin's README and changelog, the release table, the editor previews, the website bullets, and the status in docs/ideas.md.
feat(ui): MAIN and ADVANCED pages, Anvil main page around Mode, Split and Sub level
2026-11-06 21:26:59 +01:00 · 2026-11-06 21:16:11 +01:00 · 2026-11-06 21:05:31 +01:00 · 2026-11-06 21:02:52 +01:00 · 2026-11-06 17:59:07 +01:00 · 2026-11-06 17:51:19 +01:00
185 changed files with 29792 additions and 714 deletions
@@ -22,7 +22,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        plugin: [rivet, patina, anvil, crucible, lathe, temper, weld, knurl]
+        plugin: [rivet, patina, anvil, crucible, lathe, temper, weld, knurl, planish, braze, quench, ballast, forge]
    steps:
      - uses: https://github.com/actions/checkout@v4
        with:
@@ -62,6 +62,11 @@ jobs:
          cargo run --manifest-path tools/editor-check/Cargo.toml --locked -- target/editor/temper.png --plugin temper
          cargo run --manifest-path tools/editor-check/Cargo.toml --locked -- target/editor/weld.png --plugin weld
          cargo run --manifest-path tools/editor-check/Cargo.toml --locked -- target/editor/knurl.png --plugin knurl
+          cargo run --manifest-path tools/editor-check/Cargo.toml --locked -- target/editor/planish.png --plugin planish
+          cargo run --manifest-path tools/editor-check/Cargo.toml --locked -- target/editor/braze.png --plugin braze
+          cargo run --manifest-path tools/editor-check/Cargo.toml --locked -- target/editor/quench.png --plugin quench
+          cargo run --manifest-path tools/editor-check/Cargo.toml --locked -- target/editor/ballast.png --plugin ballast
+          cargo run --manifest-path tools/editor-check/Cargo.toml --locked -- target/editor/forge.png --plugin forge
      - uses: https://github.com/actions/upload-artifact@v3-node20
        with:
          name: editor-previews
@@ -93,6 +98,11 @@ jobs:
          python3 scripts/build-plugin.py --plugin temper --target x86_64-pc-windows-gnu
          python3 scripts/build-plugin.py --plugin weld --target x86_64-pc-windows-gnu
          python3 scripts/build-plugin.py --plugin knurl --target x86_64-pc-windows-gnu
+          python3 scripts/build-plugin.py --plugin planish --target x86_64-pc-windows-gnu
+          python3 scripts/build-plugin.py --plugin braze --target x86_64-pc-windows-gnu
+          python3 scripts/build-plugin.py --plugin quench --target x86_64-pc-windows-gnu
+          python3 scripts/build-plugin.py --plugin ballast --target x86_64-pc-windows-gnu
+          python3 scripts/build-plugin.py --plugin forge --target x86_64-pc-windows-gnu
          python3 scripts/package-windows.py
      - uses: https://github.com/actions/upload-artifact@v3-node20
        with:
@@ -1,7 +1,7 @@
 name: Independent plugin release
 on:
  push:
-    tags: ["rivet-v*", "patina-v*", "anvil-v*", "crucible-v*", "lathe-v*", "temper-v*", "weld-v*", "knurl-v*"]
+    tags: ["rivet-v*", "patina-v*", "anvil-v*", "crucible-v*", "lathe-v*", "temper-v*", "weld-v*", "knurl-v*", "planish-v*", "braze-v*", "quench-v*", "ballast-v*", "forge-v*"]

 permissions:
  contents: read
@@ -55,12 +55,50 @@ version = "1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f2032f911046de80f0a198e0901378627c33f59ea0ac00e363d481118bd70a53"

+[[package]]
+name = "ballast-core"
+version = "0.1.0"
+dependencies = [
+ "common-dsp",
+ "serde",
+ "serde_json",
+]
+
+[[package]]
+name = "ballast-ui"
+version = "0.1.0"
+dependencies = [
+ "ballast-core",
+ "common-dsp",
+ "common-ui",
+ "egui",
+]
+
 [[package]]
 name = "bitflags"
 version = "2.13.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3ded4057c258ba199e2d26386d3af3780957ecaee6c4ef4041c6b4b8b97c0b06"

+[[package]]
+name = "braze-core"
+version = "0.1.0"
+dependencies = [
+ "common-dsp",
+ "serde",
+ "serde_json",
+]
+
+[[package]]
+name = "braze-ui"
+version = "0.1.0"
+dependencies = [
+ "braze-core",
+ "common-dsp",
+ "common-ui",
+ "egui",
+]
+
 [[package]]
 name = "cfg-if"
 version = "1.0.5"
@@ -70,11 +108,15 @@ checksum = "4e7648175b45a9a48536d676f68d918270699102aa8dab5496df06904c914600"
 [[package]]
 name = "common-dsp"
 version = "0.1.0"
+dependencies = [
+ "serde",
+]

 [[package]]
 name = "common-ui"
 version = "0.1.0"
 dependencies = [
+ "common-dsp",
 "egui",
 ]

@@ -164,6 +206,34 @@ version = "0.31.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fc7e7a64c02cf7a5b51e745a9e45f60660a286f151c238b9d397b3e923f5082f"

+[[package]]
+name = "forge-core"
+version = "0.1.0"
+dependencies = [
+ "common-dsp",
+ "knurl-core",
+ "lathe-core",
+ "serde",
+ "serde_json",
+ "temper-core",
+]
+
+[[package]]
+name = "forge-ui"
+version = "0.1.0"
+dependencies = [
+ "common-dsp",
+ "common-ui",
+ "egui",
+ "forge-core",
+ "knurl-core",
+ "knurl-ui",
+ "lathe-core",
+ "lathe-ui",
+ "temper-core",
+ "temper-ui",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.18"
@@ -304,6 +374,7 @@ dependencies = [
 name = "patina-core"
 version = "0.2.0"
 dependencies = [
+ "common-dsp",
 "rustfft",
 "serde",
 "serde_json",
@@ -326,6 +397,25 @@ dependencies = [
 "patina-core",
 ]

+[[package]]
+name = "planish-core"
+version = "0.1.0"
+dependencies = [
+ "common-dsp",
+ "serde",
+ "serde_json",
+]
+
+[[package]]
+name = "planish-ui"
+version = "0.1.0"
+dependencies = [
+ "common-dsp",
+ "common-ui",
+ "egui",
+ "planish-core",
+]
+
 [[package]]
 name = "primal-check"
 version = "0.3.4"
@@ -350,6 +440,25 @@ version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3d595e54a326bc53c1c197b32d295e14b169e3cfeaa8dc82b529f947fba6bcf5"

+[[package]]
+name = "quench-core"
+version = "0.1.0"
+dependencies = [
+ "common-dsp",
+ "serde",
+ "serde_json",
+]
+
+[[package]]
+name = "quench-ui"
+version = "0.1.0"
+dependencies = [
+ "common-dsp",
+ "common-ui",
+ "egui",
+ "quench-core",
+]
+
 [[package]]
 name = "quote"
 version = "1.0.47"
@@ -1,7 +1,7 @@
 [workspace]
 resolver = "2"
-members = ["plugins/common/ui", "plugins/common/dsp", "plugins/anvil/core", "plugins/anvil/ui", "plugins/lathe/core", "plugins/lathe/ui", "plugins/temper/core", "plugins/temper/ui", "plugins/weld/core", "plugins/weld/ui", "plugins/knurl/core", "plugins/knurl/ui", "plugins/crucible/core", "plugins/crucible/ui", "plugins/rivet/core", "plugins/rivet/midi", "plugins/rivet/preview", "plugins/rivet/app", "plugins/patina/core", "plugins/patina/render", "plugins/patina/ui"]
-exclude = ["plugins/rivet/plugin", "tools/editor-check", "plugins/patina/plugin", "plugins/anvil/plugin", "plugins/crucible/plugin", "plugins/lathe/plugin", "plugins/temper/plugin", "plugins/weld/plugin", "plugins/knurl/plugin"]
+members = ["plugins/common/ui", "plugins/common/dsp", "plugins/anvil/core", "plugins/anvil/ui", "plugins/lathe/core", "plugins/lathe/ui", "plugins/temper/core", "plugins/temper/ui", "plugins/weld/core", "plugins/weld/ui", "plugins/knurl/core", "plugins/knurl/ui", "plugins/planish/core", "plugins/planish/ui", "plugins/braze/core", "plugins/braze/ui", "plugins/quench/core", "plugins/quench/ui", "plugins/ballast/core", "plugins/ballast/ui", "plugins/forge/core", "plugins/forge/ui", "plugins/crucible/core", "plugins/crucible/ui", "plugins/rivet/core", "plugins/rivet/midi", "plugins/rivet/preview", "plugins/rivet/app", "plugins/patina/core", "plugins/patina/render", "plugins/patina/ui"]
+exclude = ["plugins/common/params", "plugins/rivet/plugin", "tools/editor-check", "plugins/patina/plugin", "plugins/anvil/plugin", "plugins/crucible/plugin", "plugins/lathe/plugin", "plugins/temper/plugin", "plugins/weld/plugin", "plugins/knurl/plugin", "plugins/planish/plugin"]

 [workspace.package]
 edition = "2021"
@@ -26,6 +26,14 @@ opt-level = 2
 opt-level = 2
 [profile.dev.package.knurl-core]
 opt-level = 2
+[profile.dev.package.planish-core]
+opt-level = 2

 [profile.dev.package.weld-core]
 opt-level = 2
+[profile.dev.package.quench-core]
+opt-level = 2
+[profile.dev.package.ballast-core]
+opt-level = 2
+[profile.dev.package.forge-core]
+opt-level = 2
@@ -22,23 +22,31 @@ note. Each plugin is a separate product with its own version, guide and release.
 | --- | --- | --- | --- | --- |
 | **[Rivet](docs/rivet/README.md)** | Tells a MIDI motif as a story on a storyboard of roles and joins the seams into one phrase | Channel Rack | none | [Guide](docs/rivet/README.md) · [Changes](docs/rivet/CHANGELOG.md) |
 | **[Patina](docs/patina/README.md)** | Smooths harsh, ringing resonances while plain harmonic tone and transients pass | Any mixer track | one analysis frame | [Guide](docs/patina/README.md) · [Changes](docs/patina/CHANGELOG.md) |
-| **[Anvil](docs/anvil/README.md)** | Replaces the sub with a clean mono sine: one level and one start phase on every note | Bass bus | 80 ms | [Guide](docs/anvil/README.md) · [Changes](docs/anvil/CHANGELOG.md) |
+| **[Anvil](docs/anvil/README.md)** | Replaces the sub with a clean mono sine: one level and one start phase on every note, locked to the kick | Bass bus, kick as sidechain | 80 ms | [Guide](docs/anvil/README.md) · [Changes](docs/anvil/CHANGELOG.md) |
 | **[Crucible](docs/crucible/README.md)** | Records the last bars all the time, then slices, cleans and exports key-labelled samples with one button | End of the chain to resample | none | [Guide](docs/crucible/README.md) · [Changes](docs/crucible/CHANGELOG.md) |
 | **[Lathe](docs/lathe/README.md)** | EQ with one band on each harmonic of the played note: a cut on harmonic 3 stays on harmonic 3 | Bass, after the synth | ≈ 67 ms | [Guide](docs/lathe/README.md) · [Changes](docs/lathe/CHANGELOG.md) |
 | **[Temper](docs/temper/README.md)** | Distortion that drives every note the same: level and tone filters follow the note | Bass | ≈ 67 ms + oversampling | [Guide](docs/temper/README.md) · [Changes](docs/temper/CHANGELOG.md) |
 | **[Weld](docs/weld/README.md)** | Phase-aligns one bass layer to another layer through the sidechain, so the layers sum in the mids instead of cancelling | One layer's track, other layer as sidechain | none | [Guide](docs/weld/README.md) · [Changes](docs/weld/CHANGELOG.md) |
 | **[Knurl](docs/knurl/README.md)** | Gives every cycle of the note its own level, timing and grit: in-tune subharmonic growl, rattle and fry on every note | Bass | ≈ 71 ms | [Guide](docs/knurl/README.md) · [Changes](docs/knurl/CHANGELOG.md) |
+| **[Planish](docs/planish/README.md)** | Upward and downward compression (OTT) in bands set by harmonic number: band 2 holds harmonics 2–4 on every note | Bass | ≈ 67 ms | [Guide](docs/planish/README.md) · [Changes](docs/planish/CHANGELOG.md) |
+| **[Braze](docs/braze/README.md)** | Adds a detuned copy whose beating stays on the tempo grid on every note: reese movement in time | Bass | ≈ 67 ms | [Guide](docs/braze/README.md) · [Changes](docs/braze/CHANGELOG.md) |
+| **[Quench](docs/quench/README.md)** | Clips the top as hard as you like while the sub passes clean: the low end keeps its level under a loud master | Master or bass bus, last | < 1 ms (oversampling) | [Guide](docs/quench/README.md) · [Changes](docs/quench/CHANGELOG.md) |
+| **[Ballast](docs/ballast/README.md)** | Levels every note or switch-up to one loudness with a single gain each: no compression inside a part | Bass, after the sound design | ≈ 172 ms | [Guide](docs/ballast/README.md) · [Changes](docs/ballast/CHANGELOG.md) |
+| **[Forge](docs/forge/README.md)** | Lathe, Temper and Knurl as one channel strip behind one note tracker, in any order: one lookahead, and no module hears Knurl's sub-octave | Bass, after the synth | ≈ 72 ms | [Guide](docs/forge/README.md) · [Changes](docs/forge/CHANGELOG.md) |

 Plugins with latency report it to the host, so FL Studio compensates the delay.
-Anvil, Lathe, Temper and Knurl detect pitch from the audio. They can also take the
-pitch from MIDI.
+Anvil, Lathe, Temper, Knurl, Planish, Braze, Ballast and Forge detect notes from the audio. They can also take the
+pitch from MIDI. The order of the plugins matters: see [Signal chain](docs/chain.md).

 The names come from metalwork: a **rivet** joins pieces; **patina** changes a
 surface and keeps its character; an **anvil** is the solid base that everything
 is struck on; a **crucible** melts material down to be cast again; a **lathe**
 turns a piece so each cut lands the same all the way round; **tempering** sets
 how hard and how tough a metal ends up; a **weld** fuses two pieces into one;
-**knurling** presses a ridged grip pattern into a surface.
+**knurling** presses a ridged grip pattern into a surface; **planishing**
+hammers a surface smooth and even; **brazing** joins two metals with a filler; **quenching** hardens hot metal in one
+fast step; **ballast** is the weight that keeps a ship level; a **forge** is the hearth where
+every piece is heated and worked.
 The suite is the **foundry**: the workshop where the bass gets cast, shaped and
 finished. Hosts list the plugins under the vendor name *Bass Foundry*.

@@ -61,6 +69,17 @@ finished. Hosts list the plugins under the vendor name *Bass Foundry*.
    <td><a href="docs/weld/README.md"><img src="docs/weld/assets/editor.png" alt="Weld editor"></a><br><b>Weld</b>: layer phase alignment</td>
    <td><a href="docs/knurl/README.md"><img src="docs/knurl/assets/editor.png" alt="Knurl editor"></a><br><b>Knurl</b>: cycle texture</td>
  </tr>
+  <tr>
+    <td><a href="docs/planish/README.md"><img src="docs/planish/assets/editor.png" alt="Planish editor"></a><br><b>Planish</b>: harmonic OTT</td>
+    <td><a href="docs/braze/README.md"><img src="docs/braze/assets/editor.png" alt="Braze editor"></a><br><b>Braze</b>: tempo-locked beating</td>
+  </tr>
+  <tr>
+    <td><a href="docs/quench/README.md"><img src="docs/quench/assets/editor.png" alt="Quench editor"></a><br><b>Quench</b>: sub-safe clipper</td>
+    <td><a href="docs/ballast/README.md"><img src="docs/ballast/assets/editor.png" alt="Ballast editor"></a><br><b>Ballast</b>: switch-up leveller</td>
+  </tr>
+  <tr>
+    <td><a href="docs/forge/README.md"><img src="docs/forge/assets/editor.png" alt="Forge editor"></a><br><b>Forge</b>: tracked channel strip</td>
+  </tr>
 </table>

 The previews are rendered headless from the real editor code by
@@ -119,7 +138,7 @@ cargo run --manifest-path tools/editor-check/Cargo.toml -- target/editor/lathe.p
 ```

 Plugin names for the scripts are `rivet`, `patina`, `anvil`, `crucible`,
-`lathe`, `temper`, `weld` and `knurl`. Builds go to `dist/<target>/<Name>.clap`. No
+`lathe`, `temper`, `weld`, `knurl`, `planish`, `braze`, `quench`, `ballast` and `forge`. Builds go to `dist/<target>/<Name>.clap`. No
 script installs anything into a DAW. [Development and testing](docs/development.md)
 has the full command list.

@@ -157,6 +176,11 @@ plugins/
  temper/              core · ui · plugin
  weld/                core · ui · plugin
  knurl/               core · ui · plugin
+  planish/             core · ui · plugin
+  braze/               core · ui · plugin
+  quench/              core · ui · plugin
+  ballast/             core · ui · plugin
+  forge/               core · ui · plugin
  common/
    ui/                Shared look: palette, embedded fonts, knobs, panels, meters
    dsp/               Shared filters, pitch tracking, oversampling, meters, WAV files
@@ -1,5 +1,35 @@
 # Anvil changelog

+## 0.4.0
+
+- Add **Mode**: **Replace** swaps the sub as before; **Enhance** keeps the
+  original sub and adds the sine under it.
+- Add **NOTE** as a pitch source: Anvil plays a note you set, and the audio only
+  starts and stops it. Add Key lock and Follow bends for AUDIO detection.
+- Detection holds its notes: a new note needs a steady pitch for 40 ms, octave
+  jumps need 80 ms down and 200 ms up. Growls, wobbles and formant basses no
+  longer flicker between notes. Follow bends brings back the old fast behaviour.
+- When detection is unsure, Anvil plays the original sub (Enhance: adds nothing)
+  instead of a guessed note, and the NOTE readout shows **?**.
+- The editor opens on a MAIN page with Mode, Split, Sub level, Octave, Ghost,
+  Keep and Output. **ADVANCED** in the header shows every control and Kick lock.
+- Projects from 0.3 load with Replace mode, AUDIO detection, and Key lock off.
+
+## 0.3.0
+
+- Add Ghost harmonics: **Ghost** and **Ghost from** add the sub's harmonics 2–10
+  above a chosen frequency, so phones hear the note. Anvil measures the patch's own
+  harmonics above the split and fills only the ones that are missing. The sub level
+  does not change.
+- Add **Phone**, a listen mode: mono, band-limited to 400 Hz–7 kHz. Not saved.
+- Show the patch's harmonics and the added ones in an inset in the scope.
+- Add Kick lock: with the kick in the sidechain, each kick ducks the sub
+  (**Duck**, **Release**) and restarts it at Phase, shifted by **Offset**
+  (−30 to +30 ms, also before the kick).
+- Add the offset **Audition**: steps the offset from −30 to +30 ms, 4 kicks each,
+  shows how kick and sub summed per offset, and **Keep** takes the offset heard.
+- Anvil now has a sidechain input named Kick. Without Kick lock it is ignored.
+
 ## 0.2.0

 - Change the CLAP ID to `io.narl.bass-foundry.anvil`. Hosts see this as a new
@@ -1,6 +1,6 @@
 # Anvil

-Anvil gives every bass note the same solid sub. Current version **0.1.0**.
+Anvil gives every bass note the same solid sub. Current version **0.4.0**.

 In riddim and dubstep, each switch-up patch brings its own sub: a different level,
 a different phase, sometimes two layers that cancel. The drop's weight jumps from
@@ -20,42 +20,124 @@ redistributed packages.

 ## Work with it

+The editor opens on the **MAIN** page with the controls most drops need. The
+**ADVANCED** switch in the header shows every control and the Kick lock panel.
+
 1. Put Anvil on the bass bus, after the sound design and before the bus
   compression or clipping.
-2. Set **Split** just above the sub. 80–100 Hz suits most riddim basses.
-3. Set **Sub level** once. Every patch on the bus now gets this level.
-4. Use **Phase** to line the start of each note up with your kick. With
-   **Retrigger** on, every note starts at this phase.
-5. Turn on **Solo sub** to hear only the new sub; the scope shows the original
+2. Choose the **Mode**:
+   - **Replace** swaps the band below Split for the clean sine. Every note gets
+     the same level and phase. Use it when switch-ups bring different subs.
+   - **Enhance** keeps your sub as it is and adds the sine under it. Use it when
+     you like your sub and want more weight, or with **Octave** −1 for a
+     sub-octave.
+3. Set **Split** just above the sub. 80–100 Hz suits most riddim basses.
+4. Set **Sub level** once. Every patch on the bus now gets this level.
+5. In the header, set **Pitch from**. For growls and FM basses, choose **NOTE**
+   and set the drop's root. See [Pitch source](../pitch.md).
+6. On the ADVANCED page, use **Phase** to line the start of each note up with
+   your kick. With **Retrigger** on, every note starts at this phase.
+7. Turn on **Solo sub** to hear only the new sub; the scope shows the original
   low band (grey) against the new sub (accent).
+8. Turn on **Phone** to check the drop the way phones and laptop speakers play
+   it: mono, nothing below 400 Hz. A clean sub vanishes there. If the note
+   disappears with it, raise **Ghost**.
+
+When detection is unsure of the note, Anvil does not guess. In Replace mode it
+fades back to your original sub within 15 ms, and in Enhance mode it adds
+nothing. The NOTE readout shows **?** meanwhile.
+
+### Ghost harmonics
+
+Phone speakers play almost nothing below 300–500 Hz. A clean 50 Hz sub sends all
+its energy below that, so on a phone the note is gone. The ear rebuilds a note's
+pitch from its harmonics, so harmonics alone carry the note.
+
+**Ghost** adds the sub's harmonics 2–10 above **Ghost from**, falling 1/k like a
+saw. At 100 %, harmonic k sits at 2/k of the sub's level. They fade in over half
+an octave above Ghost from, and never reach below Split. The sub itself does not
+change, so the weight on a club system stays where Sub level puts it.
+
+Anvil measures each harmonic of the patch above the split and adds only what is
+missing. A harmonic the patch already has meets an added one at an unrelated
+phase and could cancel it, so Ghost leaves those alone. The inset in the scope
+shows both, per harmonic: what the patch carries (grey) and what Ghost adds
+(accent). A riddim patch usually needs little; 808s and clean sine subs need the
+most. Each new note is measured from its first 60 ms; during that time every
+harmonic counts as missing.
+
+Drive works differently: it saturates the sine itself, adds only odd harmonics,
+and changes the sub's own shape.
+
+### Kick lock
+
+With **Retrigger**, every note starts at Phase, but a kick that falls in the
+middle of a long note meets the sub at whatever phase it has reached. Kick lock
+listens to the kick through the sidechain. On each kick it dips the sub by
+**Duck** (coming back over **Release**) and restarts the sub at Phase, so the
+kick and the sub meet the same way on every hit.
+
+Set it up in FL Studio:
+
+1. Select the kick's mixer track. Right-click the route arrow under the bass
+   bus and choose **Sidechain to this track**. The kick still goes to the
+   master on its own; the sidechain only lets Anvil hear it.
+2. In Anvil's plugin wrapper, open the settings (gear icon) and set the
+   sidechain input to the kick's track.
+3. Turn on **Kick lock**. The kick count under the switch must rise with the
+   kicks.
+
+**Offset** moves the restart against the kick, from 30 ms before it to 30 ms
+after. Kicks are found on the undelayed sidechain, so with the lookahead the
+sub can restart before the kick is heard.
+
+Where the kick and sub sound like one hit is not always where they sum
+loudest: offsets one period of the note apart sum the same, and the attack of
+the kick decides where the hit is heard. So the offset is set by ear:
+
+1. Turn on **Audition** and play a loop with kicks and a long bass note. Each
+   offset from −30 to +30 ms plays for 4 kicks; the line under the bars says
+   which one plays now.
+2. Press **Keep** when kick and sub sound like one hit. Offset takes that
+   value and the audition stops.
+
+The bars show, per offset, how the kick and the sub summed below 150 Hz in the
+60 ms after each hit: +3 dB is a full sum of equal levels, 0 dB unrelated,
+below 0 dB they cancel. Use them to check the choice, not to make it.

 Other controls:

 - **Dynamics** at 0 % holds the level for the whole note. Raise it to let the sub
  follow the original's volume shape, for example a wobble.
- **Drive** adds upper harmonics so the sub reads on phones and laptops.
+- **Drive** saturates the sine: odd harmonics and a thicker sub.
 - **Octave** moves the sub against the detected note. Use −1 for a bass played
  one octave up.
 - **Glide** slides between overlapping notes; 0 jumps.
 - **Gate** is the input level that counts as a note. Raise it if tails or reverb
  start new notes.
- **Keep** blends some of the original low band back under the new sub.
+- **Keep** blends some of the original low band back under the new sub. It has
+  no effect in Enhance mode, where the original always stays.
 - **Snap to semitone** rounds detected pitch. Turn it off for pitch bends and slides.

-### Pitch from MIDI
+If Knurl is on the bass before the bus, use **MIDI**: Knurl's patterns make
+detection read notes from C2 upwards an octave low. See
+[Signal chain](../chain.md).

-Detection follows the audio by default. For heavy formant or FM basses where the
-fundamental is unclear, select **MIDI** and route the bass's MIDI notes to Anvil.
-In FL Studio, set the bass channel's MIDI output port and Anvil's input port to the
-same number, or duplicate the notes into a pattern on a channel that feeds Anvil.
+### Pitch source
+
+**Pitch from** in the header chooses where the note comes from: **AUDIO**
+detects it, **MIDI** follows MIDI notes sent to Anvil, and **NOTE** plays a note
+you set. Key lock and Follow bends tune the detection. See
+[Pitch source](../pitch.md).

 ## Timing and limits

 Detection uses 80 ms of lookahead, reported to the host for delay compensation,
 so each note's pitch is known before its attack leaves the plugin. Pitch range is
 25–250 Hz, one voice: chords and layered notes in the sub band are not separated.
-Notes shorter than about 15 ms may not be recognised. A pitch move of more than
-0.7 semitone that holds for two analysis hops (10 ms) starts a new note.
+Notes shorter than about 40 ms may not be recognised. A new pitch must hold
+steady for 40 ms to start a new note (80 ms an octave down, 200 ms an octave
+up); with Follow bends on, 10 ms. A note ends after 20 ms of silence.

 The crossover is a 4th-order Linkwitz–Riley pair, so with Keep at 100 % and no
 note playing, the signal passes with flat magnitude. Stereo above the split is
@@ -0,0 +1,25 @@
+# Ballast changelog
+
+## 0.2.0
+
+- **Parts from** defaults to **Grid**, on quarter notes. Switch-ups land on the
+  grid, and the grid needs no note detection. Saved projects keep their choice.
+- In Notes mode, detection holds its notes: a new pitch must hold for 40 ms to
+  start a new part, and a note ends after 20 ms of silence. Growls and wobbles
+  no longer split into many parts.
+
+## 0.1.0
+
+- Introduce Ballast, a switch-up leveller: every part of a bassline gets one
+  gain that brings it to the Target loudness. No compression inside a part.
+- Parts start at note starts (detected from the audio, or from MIDI) or on the
+  host's beat grid, from 1 bar to 1/16.
+- Loudness is K-weighted (ITU-R BS.1770) over each part's first 100 ms, in
+  10 ms blocks with a relative gate, and each part is weighted from rest.
+- The gain glides over 5 ms and is in place on the part's first sample.
+- **Learn** takes the next part's loudness as the target. **Amount**,
+  **Range**, **Measure from** (leave the sub out of the measurement), **Gate**,
+  **Output**, **Bypass**.
+- Editor: the last 32 parts, their loudness in and out, the target, and the
+  spread of the last 16 parts.
+- About 172 ms of latency: the tracker's lookahead, the window and the glide.
@@ -0,0 +1,84 @@
+# Ballast
+
+Ballast levels every note or switch-up of a bassline to one loudness, with a
+single gain for each. Current version **0.2.0**.
+
+Riddim and dubstep basslines change patch every few beats. Patches at the same
+peak level still differ in how loud they sound, so each switch-up lands at a
+different loudness and gets hand-set gain or clipping. A compressor would even
+them out but also change their envelope and punch. Ballast measures each part's
+loudness and gives the whole part one gain: inside a part nothing moves.
+
+![Ballast](assets/editor.png)
+
+## Install on Windows
+
+Copy `Ballast.clap` into `C:\Program Files\Common Files\CLAP\`. In FL Studio
+2024.1 or newer, open Options → Manage plugins, enable Verify plugins, and Find
+installed plugins. Load Ballast in the mixer slot of the bass, after its sound
+design. Keep the font license with redistributed packages.
+
+## Work with it
+
+1. Choose where a part starts with **Parts from**:
+   - **Grid** (the default): every line of the host's beat grid, from 1 bar to
+     1/16, quarter notes at first. Switch-ups land on the grid, and the grid
+     needs no note detection, so it also catches a patch change on the same
+     note.
+   - **Notes**: every note start, detected from the audio, or from MIDI notes
+     sent to the effect (**Notes from**: AUDIO or MIDI). Use it for basslines
+     whose parts start off the grid. A note ends after 20 ms of silence, and a
+     new pitch must hold for 40 ms to start a new part, so growls and wobbles do
+     not split into many parts. See [Pitch source](../pitch.md).
+2. Play the bassline and press **LEARN** just before the switch-up that sits
+   right in the mix. Its loudness becomes the **Target**. You can also set
+   Target by hand.
+3. Watch the display: one bar per part with its loudness as it came in, and a
+   mark where Ballast puts it. The marks line up on the target line.
+4. Lower **Amount** to keep some of the differences: 50 % halves them.
+
+The panel shows the spread of the last 16 parts, in and out: the standard
+deviation of their loudness in dB. In the editor preview four patches spread
+by 7 dB come out within 0.4 dB; the rest is what Range left.
+
+Other controls:
+
+- **Range** is the most boost or cut a part gets.
+- **Measure from**: the measurement hears only what is above this frequency;
+  the gain still applies to the whole signal. When Anvil makes the sub on the
+  bus, set it to Anvil's Split: Anvil replaces the sub anyway, so only the part
+  above it should decide the gain.
+- **Gate** is the note-start threshold (Audio). A part quieter than the gate
+  keeps the last part's gain instead of being lifted, so rests and tails are
+  not pulled up.
+- **Output** trims the level; **Bypass** crossfades to the delayed input.
+
+### How it measures
+
+A part's loudness is its K-weighted level (ITU-R BS.1770, the weighting behind
+LUFS) over its first 100 ms, or over all of it when it is shorter. The level is
+counted in 10 ms blocks, and blocks 20 dB under the part's loudest block are
+left out. Each part is weighted from rest, as if it played alone, so the last
+part's level does not ring into it.
+
+The gain glides to the new value over 5 ms and is in place on the part's first
+sample, so the attack already has the new level. Later parts of a long note keep
+that gain: Ballast does not follow the note's envelope.
+
+## Timing and limits
+
+Latency is the note tracker's lookahead (about 67 ms), the 100 ms measuring
+window and the 5 ms glide, about 172 ms in all, reported to the host for delay
+compensation. That is too much for playing live through Ballast: add it for the
+mix.
+
+In Grid mode the grid follows the host's beat position while it plays and runs
+on at the last tempo when it stops. A note start found by a change of pitch can
+come about 20 ms early, inside the gap before the note;
+the block gate keeps that gap out of the measurement. Two parts closer than
+10 ms are merged.
+
+Ballast decides from the first 100 ms of a part. A patch that swells after
+that, or a note whose loudness depends on what plays with it, is levelled by
+its start only. It levels loudness, not brightness: two patches at the same
+loudness can still differ in tone.
@@ -0,0 +1,30 @@
+# Braze changelog
+
+## 0.2.0
+
+- Add **NOTE** as a pitch source: Braze follows a note you set, and the audio
+  only starts and stops it. Add Key lock and Follow bends for AUDIO detection.
+- Detection holds its notes: a new note needs a steady pitch for 40 ms, octave
+  jumps need 80 ms down and 200 ms up. Growls, wobbles and formant basses no
+  longer flicker between notes. Follow bends brings back the old fast behaviour.
+- When detection is unsure, Braze keeps the detune of the last sure note, and
+  the readout shows **?**.
+- The editor opens on a MAIN page. **ADVANCED** in the header adds Phase, Gate
+  and Snap.
+
+## 0.1.0
+
+- Introduce Braze, a detuned copy of the bass whose beating stays on the tempo
+  grid on every note.
+- The chosen harmonic (1–8) beats once per Rate note value (1/1 to 1/32, and
+  triplets); harmonic n beats n/harmonic times as fast, so every harmonic beats
+  on the grid. The beat peaks land on the host's beat position.
+- The detune follows the tracked note. The copy jumps by exactly one period of
+  the note, so the jumps are seamless on a steady note.
+- Low cut keeps the copy out of the sub, so the sub neither beats nor changes
+  level.
+- Depth, Width (right channel's beat against the left), Phase, Gate, Output,
+  Snap to semitone, Bypass.
+- Detect pitch and note starts from the audio with about 67 ms of latency, or
+  follow MIDI notes sent to the effect.
+- Editor: one bar of the beat per harmonic with the grid and a playhead.
@@ -0,0 +1,87 @@
+# Braze
+
+Braze makes a reese's movement play in time. Current version **0.2.0**.
+
+Two layers detuned against each other beat: harmonic k of a note at f0 swells
+and fades k·f0·(r − 1) times per second, where r is the detune ratio. With a
+fixed detune that rate changes with every note, so the movement of a reese
+never lines up with the track. Braze adds a detuned copy of the bass and sets
+its detune on every note so that the beating follows the tempo.
+
+![Braze](assets/editor.png)
+
+## Install on Windows
+
+Copy `Braze.clap` into `C:\Program Files\Common Files\CLAP\`. In FL Studio 2024.1
+or newer, open Options → Manage plugins, enable Verify plugins, and Find installed
+plugins. Load Braze in the mixer slot of the bass. Keep the font license with
+redistributed packages.
+
+## Work with it
+
+The editor opens on the **MAIN** page with Rate, harmonic, Depth, Low cut, Width
+and Output. The **ADVANCED** switch in the header adds Phase, Gate and Snap.
+
+1. Put Braze on a single bass layer: a plain saw, or a reese whose own detune
+   you have turned down.
+2. Pick **Rate**: the note value one beat lasts. 1/8 at 140 BPM is 4.67 beats
+   per second.
+3. Pick the **harmonic** that should beat at Rate. Harmonic n beats
+   n/harmonic times as fast, so all of them beat on the grid: with harmonic 4 at
+   1/8, harmonic 2 beats in quarters, harmonic 8 in sixteenths, harmonic 3 in
+   quarter triplets.
+4. Set **Depth**. At 100 % the beating goes down to full nulls; 50–70 % keeps
+   the note present.
+5. On the ADVANCED page, use **Phase** to move where the beat peaks. At 0° all harmonics peak
+   together on every beat of the chosen harmonic's cycle.
+
+The display shows one bar: a row per harmonic with the level it gets from the
+beating, the grid at Rate, and the playhead.
+
+Other controls:
+
+- **Low cut** removes the copy below a frequency, so the sub does not beat.
+  The sub keeps its level. Harmonics under the cut show *cut* in the display.
+  Under 20 Hz the cut is off. If the chosen harmonic is under the cut on a
+  note, it does not beat: the note panel says so; pick a higher harmonic.
+- **Width** moves the right channel's beat against the left, up to half a
+  cycle. At 100 % one side peaks while the other nulls. Check the mono sum.
+- **Gate** is the input level that counts as a note.
+- **Snap to semitone** rounds the detected pitch. Leave it off on detuned or
+  bent notes: the copy jumps by one period of the pitch in use.
+
+### Pitch source
+
+**Pitch from** in the header chooses where the note comes from: **AUDIO**
+detects it, **MIDI** follows MIDI notes sent to Braze, and **NOTE** uses a note
+you set. For heavy FM, formant or noise basses, NOTE with the drop's root is the
+safest choice. Key lock and Follow bends tune the detection. While detection is unsure of the note, Braze keeps the detune of the last sure note and the readout shows **?**. See
+[Pitch source](../pitch.md).
+
+### How the detune is made
+
+The copy is the bass read from a delay line. Its delay falls by one period of
+the note per beat cycle of the chosen harmonic, which tunes the copy up by
+exactly r = 1 + B/(k·f0) (B: beats per second, k: the chosen harmonic). When it
+has fallen a whole period, it jumps back by one period: on a steady note both
+read positions hold the same waveform, so the jump is crossfaded over 6 ms
+without a seam. At a beat peak the copy lines up with the bass sample for
+sample.
+
+The low detune that low notes need is large: harmonic 1 at 1/8 and 140 BPM on
+F1 (43.7 Hz) is r = 1.107, about 1.8 semitones. Higher harmonics need less:
+harmonic 4 asks for about 45 cents on F1.
+
+## Timing and limits
+
+Detection uses about 67 ms of lookahead, reported to the host for delay
+compensation. Pitch range is 30–500 Hz, one voice. The beat position comes from
+the host while it plays, shifted by the lookahead so the beat stays on the
+timeline. When the host is stopped, the beat runs on freely at the last tempo.
+
+Noise, chords and the attack of a note are not periodic, so the copy's jumps
+are heard there as a short blur. Before the first note, the copy assumes 55 Hz.
+
+Braze changes the waveform in time, so pitch detection after it can be less
+sure: put tracked plugins before Braze, or use MIDI or NOTE. See
+[Signal chain](../chain.md).
@@ -0,0 +1,78 @@
+# Signal chain
+
+The order of the Bass Foundry plugins in a chain matters. Anvil, Lathe, Temper,
+Knurl, Planish, Braze, Ballast and Forge each detect the pitch from the audio they receive. If a plugin earlier
+in the chain changes the audio, the pitch detection after it can go wrong.
+
+## Recommended order
+
+```text
+bass track:   synth → Lathe → Temper → Planish → Braze → Knurl → Patina → Ballast → Weld
+  or:         synth → Forge (Lathe, Temper, Knurl) → Planish → Braze → Patina → Ballast → Weld
+bass bus:     Anvil → (bus compression) → Quench → Crucible
+master:       … → Quench (last, or before a true-peak limiter)
+```
+
+- **Lathe and Temper before Knurl.** They hear the plain synth, where the pitch
+  is clear.
+- **Or Forge in their place.** Forge runs Lathe, Temper and Knurl behind one
+  tracker that reads its input, so the order inside it does not upset the pitch
+  detection, and the three cost one lookahead (about 72 ms) instead of three.
+  Planish and Braze then come after Knurl: run them from MIDI.
+- **Planish after the distortion, before Knurl.** OTT usually comes after
+  distortion. Planish's band edges follow the tracked note, so it also needs a
+  clear pitch: after Knurl, use MIDI.
+- **Braze after Planish.** Its copy beats against the bass, so a pitch
+  detector after it is less sure: Knurl after Braze works best in MIDI mode.
+  Weld after Braze sees the beating as a looser match between the layers; if
+  it reads Loose, move Braze to the bus after Anvil, with Low cut at or above
+  Anvil's Split. There it reads the pitch from Anvil's clean sub, and the sub
+  stays out of the beating.
+- **Ballast after the sound design.** It levels what the patch finally sounds
+  like, so it comes after the distortion, OTT and Patina. It finds note starts
+  like the other tracked plugins: after Knurl, use MIDI or Grid. Weld and Anvil
+  come after it. On the bus with Anvil, set Measure from to Anvil's Split.
+- **Knurl last among the pitch-tracked plugins.** See below. Ballast only
+  needs note starts; after Knurl, run it from MIDI or the grid.
+- **Patina after the tracked plugins.** It does not detect pitch, so the order
+  does not change its result.
+- **Weld after every plugin with latency on its track.** Weld can delay its own
+  layer but cannot move it earlier. If FL Studio does not compensate the
+  sidechain route, any latency added after Weld's input on the main layer makes
+  that layer late.
+- **Anvil on the bus, in MIDI mode when Knurl is in the chain.** For Kick
+  lock, send the kick's track to Anvil as a sidechain.
+- **Quench last on the bus or the master.** It clips the top and leaves the sub
+  alone, so put it where you would put a clipper. On the bass bus after Anvil,
+  set its Split at or a little above Anvil's Split: Anvil's sub then passes
+  Quench untouched. Quench does not detect pitch, so it can sit after Knurl.
+- **Crucible at the end of the chain you want to resample.**
+
+## Knurl and pitch detection
+
+Knurl's patterns make every second (or third) cycle quieter. That is a real
+sub-octave in the signal, so a pitch detector after Knurl hears the note one
+octave low, or with Triple an octave and a fifth low. Measured with the suite's
+tracker on a saw bass:
+
+- From C2 (65 Hz) upwards, Double, Fry (the default), Triple and Gallop make
+  the detector read the wrong octave for about 85 % of the note.
+- Below C2 the false sub-octave is under 30 Hz, out of the detection range, so
+  low notes are tracked correctly.
+- Level and time jitter add 5–25 false note starts per second. Anvil restarts
+  its phase on each, Lathe, Temper and Planish retune on each.
+
+When a tracked plugin must come after Knurl, select **MIDI** as its pitch source
+and route the bass's MIDI notes to it. Inside Forge this does not apply: its one
+tracker reads the input before Knurl.
+
+## Latency
+
+Each tracked plugin adds its own lookahead: Anvil 80 ms, Lathe, Temper,
+Planish and Braze about 67 ms, Knurl about 71 ms, Patina about 45 ms, Ballast
+about 172 ms, Quench under 1 ms. Forge holds Lathe, Temper and Knurl in about
+72 ms, against about 206 ms for the three plugins in a row. A full chain is
+about 400 ms. FL
+Studio compensates this for playback and rendering, but playing a MIDI keyboard
+through the full chain is not practical. Write with a shorter chain and add the
+rest for the mix.
@@ -1,5 +1,20 @@
 # Crucible changelog

+## 0.4.0
+
+- A slice is named by a note only when at least three in five pitch reads over
+  its body agree on it. Growls, slides and noise are saved without a note
+  instead of with a wrong one.
+- Add the song **Key**: slice names use its spelling, such as Ab instead of G#.
+  Without a key, names use sharps as before.
+
+## 0.3.0
+
+- **Keep takes** (on by default) saves every capture's loop to a `takes`
+  subfolder of the export folder at once. Takes are still not part of the
+  project, but a reload or a crash no longer loses them. Existing files are
+  never overwritten.
+
 ## 0.2.0

 - Change the CLAP ID to `io.narl.bass-foundry.crucible`. Hosts see this as a new
@@ -1,7 +1,7 @@
 # Crucible

 Crucible melts the bars you just played into ready-to-use samples. Current version
-**0.1.0**.
+**0.4.0**.

 Resampling is the core loop of riddim sound design: bounce, open in Edison, chop,
 trim, declick, normalise, find the key, name, save, load into a sampler. Crucible
@@ -33,7 +33,11 @@ Each export creates a folder named after the date, time and tempo, holding:

 - `loop.wav`: the whole take, for Slicex or Edison;
 - `s01_F1.wav`, `s02_G#1.wav`, …: one file per slice, named by its detected root
-  note. The root is also stored in the file's sampler chunk;
+  note. The root is also stored in the file's sampler chunk. A slice gets a
+  note only when most of it holds one clear pitch; a growl, a slide or noise is
+  saved as `s03.wav`, because a wrong note name is worse than none. Choose the
+  song's **Key** to spell the names in it: in F minor a slice is `s02_Ab1.wav`,
+  not `s02_G#1.wav`. Without a key, names use sharps;
 - `wavetable.wav` when **Wavetable** is on: up to 256 single-cycle frames of 2048
  samples from the selected slice. Each frame starts on a rising zero crossing, so
  frames morph without phase jumps. Serum reads the frame size from the file; in
@@ -52,9 +56,14 @@ the playlist or Edison. **Open folder** shows the latest export in Explorer.
 Crucible adds no latency and passes audio through untouched. Auditioned slices are
 mixed into its output only while they play. The history holds 72 s, enough for
 16 bars at 60 BPM. The newest eight takes stay in memory until the plugin is
-removed; they are not saved with the project, so export what you want to keep.
+removed; they are not saved with the project. With **Keep takes** on (the
+default), every capture's loop is also written at once to
+`takes/<date>_<time>_<tempo>bpm_<bars>bars.wav` in the export folder, so a reload
+or a crash loses nothing. Existing files are never overwritten.

 Bar alignment follows the host's song position and time signature. Root notes are
-detected between 35 Hz and 1 kHz. Unpitched slices, such as drums or noise, get
-no note in their name. Transient slicing finds hits that rise out of quieter
+detected between 35 Hz and 1 kHz. The pitch is read at up to 12 points across
+each slice after its attack; at least three reads in five must be clear and on
+the same note. Unpitched slices, such as drums
+or noise, get no note in their name. Transient slicing finds hits that rise out of quieter
 audio; for legato basses, slice on the grid.
@@ -25,7 +25,10 @@ Patina has `render` for offline WAV evaluation. The shared crates are:

 - `common-ui`: palette, embedded fonts, header, panels, knobs, meters.
 - `common-dsp`: filters, YIN pitch tracking, the note tracker used by Anvil,
-  Lathe, Temper and Knurl, 4× oversampling, meters and WAV files.
+  Lathe, Temper, Knurl, Planish, Braze, Ballast and Forge (with the `Tracked`
+  module trait that lets Lathe, Temper and Knurl run behind one shared tracker),
+  4× oversampling (also Quench's), BS.1770 K-weighting (Ballast), meters and WAV
+  files.

 The wrappers stay separate workspaces, each with its own lockfile, so the
 NIH-plug Git dependency stays out of the root workspace. Host identities and
@@ -45,7 +48,7 @@ python3 -m unittest discover -s scripts/tests -v
 ```

 Products: `rivet`, `patina`, `anvil`, `crucible`, `lathe`, `temper`, `weld`,
-`knurl`.
+`knurl`, `planish`, `braze`, `quench`, `ballast`, `forge`.

 `check-plugin.py` runs formatting, tests and clippy for one product's packages
 and its wrapper, without compiling the other products. Run it for every product
@@ -144,6 +147,11 @@ identify plugins by CLAP ID, so the vendor name does not affect saved projects.
 | Temper | (new) | `io.narl.bass-foundry.temper` |
 | Weld | (new) | `io.narl.bass-foundry.weld` |
 | Knurl | (new) | `io.narl.bass-foundry.knurl` |
+| Planish | (new) | `io.narl.bass-foundry.planish` |
+| Braze | (new) | `io.narl.bass-foundry.braze` |
+| Quench | (new) | `io.narl.bass-foundry.quench` |
+| Ballast | (new) | `io.narl.bass-foundry.ballast` |
+| Forge | (new) | `io.narl.bass-foundry.forge` |

 CLAP IDs use the form `io.narl.bass-foundry.<product>`. Builds tagged before
 this scheme used `io.storyboard.*` IDs; hosts treat the new IDs as different
@@ -0,0 +1,26 @@
+# Forge changelog
+
+## 0.2.0
+
+- Add **NOTE** as a pitch source: Forge follows a note you set, and the audio
+  only starts and stops it. Add Key lock and Follow bends for AUDIO detection.
+- Detection holds its notes: a new note needs a steady pitch for 40 ms, octave
+  jumps need 80 ms down and 200 ms up. Growls, wobbles and formant basses no
+  longer flicker between notes. Follow bends brings back the old fast behaviour.
+- All modules share the pitch source, Key lock and Follow bends.
+- When detection is unsure, each module acts as its standalone plugin: Lathe
+  passes the audio, Temper keeps its tuning, Knurl fades its texture out.
+- Each module page opens on its MAIN controls. **ADVANCED** in the header shows
+  every control on all pages.
+
+## 0.1.0
+
+- Introduce Forge, one tracked channel strip: Lathe, Temper and Knurl behind a
+  single note tracker, in any of the six orders, each module on or off.
+- Every module follows the note read from the strip's input, so a module after
+  Knurl no longer hears Knurl's sub-octave.
+- One latency of about 72 ms, the same in every order, instead of more than
+  200 ms for the three plugins in a row.
+- A single module on its own gives the same output, sample for sample, as its
+  standalone plugin.
+- Editor: the chain, and each module's standalone editor as its page.
@@ -0,0 +1,70 @@
+# Forge
+
+Forge is one tracked channel strip: Lathe, Temper and Knurl run behind a single
+note tracker, in the order you choose. Current version **0.2.0**.
+
+Each of the three plugins detects the played note itself. In a row, their
+lookaheads add up (Lathe 67 ms, Temper 68 ms, Knurl 71 ms: more than 200 ms),
+and a tracker after Knurl hears Knurl's sub-octave and follows a note an octave
+low. Forge reads the note once, from its input, and every module follows that
+one tracker. In a test with Knurl's sub-octave pattern in front of Lathe, a
+standalone Lathe after Knurl followed the note an octave low in every frame;
+Lathe inside Forge followed the played note in every frame.
+
+![Forge](assets/editor.png)
+
+## Install on Windows
+
+Copy `Forge.clap` into `C:\Program Files\Common Files\CLAP\`. In FL Studio
+2024.1 or newer, open Options → Manage plugins, enable Verify plugins, and Find
+installed plugins. Load Forge in the mixer slot of the bass, right after the
+synth. Keep the font license with redistributed packages.
+
+## Work with it
+
+1. Choose **Pitch from** in the header: **AUDIO** detects the note from the
+   input; **MIDI** follows MIDI notes sent to the effect; **NOTE** uses a note
+   you set. All modules use it, with the same Key lock and Follow bends. See
+   [Pitch source](../pitch.md).
+2. The **Chain** row shows the modules in processing order. Click a module's
+   name to edit it below; **ON** switches it on or off. The button between two
+   modules swaps them. The default order is Lathe, Temper, Knurl, as in the
+   standalone chain.
+3. Each module's page is its standalone editor: [Lathe](../lathe/README.md),
+   [Temper](../temper/README.md) and [Knurl](../knurl/README.md) explain the
+   controls. Each page opens on its MAIN controls; the **ADVANCED** switch in
+   the header shows every control on all pages. Temper's **AUTO GAIN** sits in
+   the Chain row while its page is open.
+4. The **Gate** knob on every page is the one shared tracker gate: turning it on
+   one page turns it on all.
+
+**Bypass** in the header crossfades the whole strip to the delayed input.
+
+While detection is unsure of the note, each module does what its standalone
+plugin does: Lathe passes the audio, Temper keeps the last sure tuning, and
+Knurl fades its texture out.
+
+## How it works
+
+The tracker reads the strip's input, and the audio is delayed by its lookahead
+once. Every module gets the note events delayed by the latency of the modules
+in front of it, so each module sees a note start exactly on the attack of the
+audio it receives. A single module on its own in Forge gives the same output,
+sample for sample, as its standalone plugin, in every position of the chain.
+
+Temper's **Normalize** measures each note's level one lookahead ahead. In Forge
+it measures the strip's input, not the output of the modules in front of it.
+Lathe and Knurl change the level about equally on every note, so the notes
+still reach the shaper at one level.
+
+## Timing and limits
+
+Latency is the tracker's lookahead (about 67 ms), Temper's oversampling filters
+(under 1 ms) and Knurl's room for timing jitter (about 4 ms): about 72 ms in
+all, reported to the host. A module that is off still delays its audio by its
+own latency, so the latency stays the same in every order and with any module
+off.
+
+Changing the order while audio plays switches the routing at once and can
+click. The standalone plugins stay: use them when you need only one module, or
+when another plugin must sit between two of them.
@@ -35,6 +35,283 @@ Each entry names the problem first. Entries are grouped as released or idea. Nam
    automation lanes or chopping.
 15. There is no meter for texture. Two switch-ups can sound "the same" without
    a clear reason, and generic analysers show only level and spectrum.
+16. OTT and multiband compression use fixed band edges, so the same setting
+    squashes different harmonics on every note.
+17. Riddim masters rely on clipping. A clipper that also clips the sub turns
+    the low end into distortion.
+18. Resampled basslines have no MIDI, so tools that need the notes have nothing
+    to follow.
+19. A clean sub carries the note on a club system but vanishes on phones and
+    laptops. Distortion makes the note readable there, but also changes the
+    patch.
+20. Detuned layers (reese) beat at a rate that changes with every note and every
+    harmonic, so the movement is never in time with the track.
+21. Kick and sub on the same MIDI tick are not heard at the same moment: the
+    heard hit depends on the attack shapes and on the offset between them.
+
+## Signal flow and suite audit (2026-11)
+
+How the released plugins fit into one production:
+
+```text
+WRITE      Rivet (motif → storyboard) ──MIDI──► synth
+DESIGN     synth → Lathe → Temper → Knurl → Patina
+RESAMPLE   Crucible (capture → slice → export) ──► sampler / wavetable synth ──► DESIGN
+LAYER      layer A + layer B → Weld (mids) → bass bus → Anvil (sub)
+MIX        gap: loudness, clipping, OTT, mono check, kick against sub, reference
+```
+
+Writing and sound design are covered. Mixing and mastering have only Anvil and
+Patina. Findings from the audit:
+
+- **Latency adds up.** A full chain (Knurl 71 + Temper 67 + Lathe 67 + Patina
+  about 45 + Anvil 80 ms) is about 330 ms. FL Studio compensates it for
+  playback, but a chain this long cannot be played live.
+- **MIDI mode keeps the lookahead.** `Tracker::latency()` depends on the pitch
+  range only. With MIDI as the source, the note is known at its attack, so the
+  lookahead could be close to zero. This needs a latency change at runtime,
+  which must be checked in FL Studio first.
+- **Knurl confuses every tracker after it.** Measured: Knurl output fed into
+  `TrackerConfig::BASS`. From C2 (65 Hz) upwards, Double, Fry (the default),
+  Gallop and Triple make the next tracker read the note one octave (Triple:
+  an octave and a fifth) too low for about 85 % of the note. Below C2 the false
+  sub-octave is under 30 Hz, out of range, so low notes are safe. Level and time
+  jitter also cause 5–25 false note starts per second. Anvil on the bus after
+  Knurl then plays the sub an octave low and restarts its phase. Until there is
+  a shared tracker: put Knurl after the other tracked plugins, and use MIDI as
+  the source for any tracked plugin after Knurl. See [Signal chain](chain.md).
+- **Each tracked plugin needs its own MIDI route.** Four plugins in MIDI mode
+  are four FL routing setups.
+- **Weld and delay compensation are untested together.** If the main layer's
+  chain has more latency than the sidechain layer and FL does not compensate
+  the sidechain route, the main layer arrives late, which an allpass cannot
+  fix. Put Weld after every plugin with latency on that track.
+- **Crucible lost takes on reload.** Takes are not saved with the project.
+  Fixed: Keep takes writes every capture's loop to disk at once.
+- **Settings handling differs.** Patina has presets and A/B; the others do not.
+  Lathe's drawn gains and Knurl's drawn pattern cannot be automated.
+
+## Producer feedback (2026-11-06)
+
+Feedback from producers who tried the suite: most plugins are confusing to use.
+One example: "why does it try to detect the key? It switches around fast,
+because sounds usually aren't just one kind of note." Anvil "was kind of cool,
+but didn't do what we expected." Patina's feedback (threshold, ratio) is handled
+in Patina 0.5.0.
+
+### What goes wrong
+
+1. **Nine of thirteen plugins depend on one hidden guess: the note.** Anvil,
+   Lathe, Temper, Knurl, Planish, Braze, Forge, Ballast (Notes mode) and
+   Crucible (file names) all read the pitch from the audio. Patina's Tone guard
+   also does, but it is off by default. Our tests use saws and sines, where
+   tracking is perfect. Real riddim basses are FM growls, formant sweeps, noise,
+   pitch drops, stacked octaves and layers. On those, "the note" is often not
+   one note.
+2. **The tracker is built to react fast, not to stay put.** In
+   `common-dsp/src/tracker.rs`, a move of 0.7 semitone that holds for two 5 ms
+   hops starts a new note. Smaller moves retune every 5 ms. Frames below
+   clarity 0.5 are skipped, but the last guess stays in use. On a growl, the
+   formant and FM movement reads as a pitch moving every few milliseconds, and
+   octave errors count as new notes. The NOTE readout flickers, and everything
+   tuned to the note moves with it. That is the "switches around fast".
+3. **A wrong guess is worse than no guess.** When tracking is wrong, a tracked
+   plugin does something no normal plugin would do:
+   - Anvil plays a sub at the wrong pitch.
+   - Lathe moves its bands onto the wrong frequencies.
+   - Temper's Floor, Push and Bright filters jump.
+   - Planish's band edges jump, so the bands pump.
+   - Braze's beating leaves the grid.
+   - Knurl's cycle clock runs at the wrong rate.
+   - Crucible names a slice after a note it is not.
+   A producer cannot tell this from "the plugin is broken".
+4. **The plugins explain themselves in DSP terms.** Harmonic numbers, cycles,
+   periods, splits, phase and allpass sections. A producer reads the category
+   ("EQ", "distortion", "OTT", "sub") and expects that behaviour. When the
+   tracked behaviour differs, it feels random.
+5. **The escape route is hidden.** MIDI as the pitch source fixes the guess,
+   but in FL Studio it needs the channel's MIDI output port and the effect's
+   input port set to the same number. Few producers know how to do that.
+6. **Panels show everything at once.** Most plugins put 10–20 controls on the
+   front panel, with equal weight. The one or two that matter for the first
+   result do not stand out.
+
+### Principles for the next round
+
+- **Never act on a guess you are unsure of.** Every tracked plugin falls back
+  to something neutral when tracking is unsure: pass the audio through, keep
+  the original sub, or use fixed-Hz settings. It does not fall back to the last
+  guess. Show this state: the NOTE readout dims or shows "—".
+- **Stable by default.** A new note needs a confident pitch held for 40–60 ms.
+  An octave jump needs longer still. Inside a note, the tuning holds and does
+  not retune every hop, unless the user turns on "Follow bends".
+- **Let the producer say the note.** Add a third pitch source next to AUDIO and
+  MIDI: **NOTE** or **KEY**. The producer picks the root (for example F), and
+  the plugin uses it with no detection at all. Most riddim drops sit on one or
+  two roots. A scale lock goes in between: detection may only pick notes in the
+  chosen key. This removes the micro-jumps and most wrong notes.
+- **Name controls by outcome, not by mechanism.** Use names like "Sub level"
+  and "Tighten". Show one big main control per plugin, and move the rest under
+  an "Advanced" fold.
+- **Test on real material.** Collect 5–10 short stems: a growl, an FM bass, a
+  reese, an 808 with a slide, a formant bass, a layered drop, a noise riser.
+  Add a tracker metric for note changes per second and the share of time the
+  tracker is wrong or unsure. Every tracker change must lower it on the stems,
+  not only pass the saw tests.
+
+### Per plugin
+
+- **Anvil.** It does not do what producers expected. The candidates are below;
+  ask the tester which one they meant.
+  - (a) They expected a sub *enhancer*: add weight under the existing sound,
+    not replace it.
+  - (b) They expected it to follow their growl, and it played wrong sub notes.
+    The wrong sub notes are the worst failure in the suite.
+  - (c) They expected a simple "fix my low end" (mono, tight, level), and the
+    front panel offers Phase, Retrigger, Kick lock, Ghost and Audition.
+  Fixes:
+  - Keep the original sub (Keep 100 %) whenever tracking is unsure, and switch
+    to the clean sine only on a confident note.
+  - Add the NOTE source with a root picker.
+  - Add an Enhance mode that adds the sine under the original instead of
+    replacing it.
+  - Keep three main controls: Split, Sub level, Mode. Fold the rest.
+- **Lathe.** A harmonic EQ is a new idea for most producers. Show the band
+  centres in Hz on the plot, next to the harmonic numbers. When tracking is
+  unsure, pass the audio through.
+- **Temper.** Producers judge it as distortion first. Floor, Push and Bright
+  should keep their last confident tuning, or fall back to fixed Hz, instead of
+  jumping. Consider Floor/Bright with fixed-Hz values as the default, and
+  tracked values as an option.
+- **Knurl.** It needs the cycle clock, so it needs a pitch. NOTE mode and
+  fade-out on unsure tracking matter most here.
+- **Planish.** When tracking is unsure, fall back to fixed band edges (like OTT)
+  instead of jumping. Crossfade the edges when the note changes.
+- **Braze.** It needs a pitch. Use NOTE mode, hold the detune through unsure
+  stretches, and do not jump.
+- **Ballast.** Make **Grid** the default for Parts from. A switch-up lands on
+  the grid, and Grid needs no tracking.
+- **Crucible.** Name a slice by its note only when one note is confident over
+  most of the slice. Otherwise leave the note out (or write "?"). An optional
+  song key field avoids enharmonic names that do not fit the key.
+- **Forge.** It inherits everything above from the shared tracker.
+- **Weld, Quench, Patina.** These use no tracking by default. Weld's display is
+  dense: lead with Recovered dB and one ALIGN button, and fold the plots.
+
+### Order
+
+1. Shared tracker: confidence, stability and hold, plus the stem corpus and
+   metric. One change in `common-dsp` fixes the flicker in nine plugins.
+2. NOTE/KEY pitch source in the shared tracker settings and in each tracked
+   plugin's header.
+3. "Unsure means neutral" fallback in each tracked plugin, Anvil first.
+4. Anvil Enhance mode and a reduced front panel. Ask the tester what they
+   expected first.
+5. Front-panel pass on every plugin: a main control, outcome names, and an
+   Advanced fold.
+
+### Status (2026-11-06)
+
+Done in Anvil 0.4.0, Lathe 0.3.0, Temper 0.3.0, Knurl 0.3.0, Planish 0.2.0,
+Braze 0.2.0, Ballast 0.2.0, Forge 0.2.0, Crucible 0.4.0 and Weld 0.4.0. Not
+tested in FL Studio yet, and the tester has not been asked which Anvil they
+expected.
+
+1. Done. The tracker needs a steady pitch for 40 ms to start a note (80 ms an
+   octave down, 200 ms up), holds within a quarter semitone, ends a note after
+   20 ms of silence, and reports unsure after about 40 ms of disagreeing reads.
+   Follow bends keeps the old fast behaviour. The corpus is synthetic
+   (`common-dsp/src/stems.rs`, `examples/tracker_report.rs`): extra note starts
+   per second on formant, wobble and reese fell from 28.5, 11.8 and 1.3 to 0.
+   Wobble is still unsure 37 % of the time and the hard growl 4.5 %.
+2. Done: NOTE source with a note picker, Key lock (minor, major, root only) and
+   Follow bends, shared through `common-params`. Ballast has no NOTE: its parts
+   need note starts from the audio or MIDI.
+3. Done. Anvil plays the original sub, Lathe passes the audio, Knurl fades out,
+   Temper, Planish and Braze hold the last sure note. Planish slides its edges
+   over 6 ms on a new note. Crucible names slices only on a sure note and
+   spells them for a song key.
+4. Done: Replace / Enhance mode, and a MAIN page with Mode, Split and Sub level.
+5. Done for Anvil, Lathe, Temper, Knurl, Planish, Braze, Forge and Weld: a MAIN
+   page and an ADVANCED switch. Lathe labels harmonics in Hz. Ballast defaults
+   to Grid.
+
+Still open:
+
+- Real stems. Score the tracker on 5–10 real drops with `tracker_report` and
+  tune on those, not only on the synthetic corpus.
+- Outcome names. Controls keep their old names; only the pages changed.
+- Temper with fixed-Hz Floor and Bright as the default.
+- Weld's single ALIGN button.
+- Panel pass for Quench, Patina, Crucible, Rivet and Ballast. Their panels were
+  already short, so they were left as they are.
+- `tools/editor-check` has a clippy `chunks_exact` lint outside the plugin
+  checks.
+
+## Research findings (2026-11)
+
+From the papers in `research/` (local, not committed). Each finding names where
+it goes in the suite. They are starting points to test by ear, not rules.
+
+- **A published bass fatness model.** Schmedeke's dissertation (Hamburg 2021,
+  "BASS DROP!", section 5.4.3) models momentary fatness of dance-music excerpts
+  over 50 ms windows from two inputs only, with adjusted R² 0.773:
+  `l = 10 / (1 + 4.5487·exp(0.13·(62.9366 − SPL<200)))`,
+  `h = 10 / (1 + 1.4317·exp(2.5575·(0.3299 − HR<200)))`,
+  `Fat = 0.14689·l·h` (0 to 14.7). SPL<200 is the C-weighted level below
+  200 Hz in dB(C) with the material normalised to −23 LUFS; HR<200 is the
+  MPEG-7 harmonic ratio (how periodic) of the same band. Chapter 4's earlier
+  linear model on synthetic tones (R² 0.597) points the same way: a tonal low
+  band is fatter, a noisy one is not. Anvil's clean sine maximises HR; Quench
+  keeps it when the top is clipped. The thesis does not state the dB(C) of its
+  reference, so the dBFS-to-dB(C) offset is an assumption. Measured with
+  `scripts/fatness.py` on the seven Devath references (offset 100 dB): drops
+  sit at 4–6, breakdowns near 0, kick gaps show as 50 ms dips; SPL<200 medians
+  are 67–69 dB(C), a few dB under the thesis's "mostly 70–80", so the offset
+  may be 2–5 dB low. Goes into Assay as one lane, never as an overall score.
+- **Virtual bass from known harmonics.** Moliner, Rämö and Välimäki (DAFx 2020)
+  boost the harmonics that exist with weights that follow the sound's spectral
+  envelope (limits 10 dB/oct below, 3 dB/oct above) and generate the missing
+  ones, so a small speaker suggests the fundamental. Their nonlinear stage fails
+  intermodulation tests, so they use it on transients only. The suite knows f0,
+  so it can add harmonics at exactly k·f0 with no intermodulation (problem 19).
+  Anvil's sub is a pure sine, so Lathe has no harmonics there to boost.
+- **Group-delay audibility.** Liski, Mäkivirta and Välimäki (2021): between
+  500 Hz and 4 kHz, listeners hear a group-delay peak from about 0.64 ms
+  (positive) or 0.56 ms (negative) on clicks over headphones; a fast-decaying
+  hi-hat hides it. Weld's allpass sections add positive group delay there.
+  Done: Weld shows the delay spread (released in 0.3.0). Measured: common fits from
+  Weld's own tests spread 0.82–1.03 ms, above the click threshold, so the
+  display gives a note, not a warning.
+- **Timbral tension.** Farbood and Price (2017): more roughness, inharmonicity
+  and spectral flatness raise judged tension; brightness (centroid) gives no
+  clear result. These are the measures planned for Loupe, and the controls a
+  tension macro would move.
+- **Coupled one-knob controls.** A 2026 distance renderer derives five distance
+  cues from one control, so they always agree; in its listening test it roughly
+  halved placement error and every participant preferred it. A pattern for
+  macros in Forge.
+- **Shared motion binds layers.** Temporal coherence (Elhilali et al. 2009) is
+  a grouping cue: sub, body and top sound like one sound when their main
+  movements line up. One modulation source inside Forge gives that by
+  construction; across separate `.clap` files it needs the shared memory
+  rejected below.
+- **Heard timing of layered hits.** Danielsen et al. (2026): attack shape and
+  the offset between two layers together set when the compound hit is heard
+  and whether it fuses. Hove et al. (2014): timing deviations are heard more
+  clearly in lower voices, so the bass sets the grid (problem 21).
+- **Loopback FM.** Smyth (DAFx 2026): an oscillator that frequency-modulates
+  itself shifts its own sounding pitch as feedback rises. Her closed-form
+  solution gives the sounding frequency, so a growl can stay on the tracked
+  note at any feedback.
+- **Beating depends on note and harmonic.** For two layers detuned by ratio r,
+  harmonic k beats at k·f0·(r − 1) Hz (Plomp and Levelt 1965 for the roughness
+  context). Fixed cents beat faster up the keyboard; fixed Hz beats the same on
+  every harmonic (problem 20).
+- **Do not encode as rules:** a best sub frequency, crossover or kick/bass
+  offset; one number for loudness, roughness, groove and preference; random
+  jitter sold as humanisation; more harmonics sold as more physical bass;
+  largest correlation sold as the best alignment.

 ## Released

@@ -42,7 +319,8 @@ Each entry names the problem first. Entries are grouped as released or idea. Nam

 Replaces the band below a split frequency with a clean mono sine that follows
 the bass pitch, at one level and one start phase for every note. Pitch comes
-from detection with 80 ms lookahead or from MIDI. See [Anvil](anvil/README.md).
+from detection with 80 ms lookahead, from MIDI, or from a set note. Enhance
+mode adds the sine under the original sub instead. See [Anvil](anvil/README.md).

 ### Crucible — resampler (problem 3)

@@ -83,8 +361,208 @@ burst per cycle tuned to the note. Amounts are counted in cycles, so the texture
 is the same on every note. Slow per-harmonic drift is postponed. See
 [Knurl](knurl/README.md).

+### Planish — harmonic OTT (problem 16)
+
+Upward and downward compression in four bands whose edges are harmonic numbers
+of the tracked note (default 1, 2–4, 5–16, 17 and up), so the same setting
+squashes the same harmonics on every note. Each band's level is measured over
+one period of the note, so heavy settings do not ripple at f0. See [Planish](planish/README.md).
+
+## Next for released plugins
+
+- **Anvil**: *Kick lock* and the *offset audition* are done (Anvil 0.3.0, see
+  [Anvil](anvil/README.md)): the kick through the sidechain ducks the sub and
+  restarts its phase at an offset (problem 6); the audition steps −30 to +30 ms,
+  4 kicks each, Keep takes the offset heard, and the low-band sum per offset is
+  shown apart from that choice (problem 21). Measured on a 55 Hz kick burst
+  against a 55 Hz sub: +2.4 dB at 0 ms, −4.6 dB at −10 ms, −5.9 dB at +10 ms,
+  and +1.8 to +2.2 dB again one period away (±20 ms), so the sum alone cannot
+  pick the hit. Open: a finer second sweep around the kept offset; a gate or
+  sensitivity for kicks with long tails or a kick bus with other drums.
+  A sub shape from sine to rounded
+  triangle. A note attack counted in cycles. *Ghost harmonics* and the
+  *Phone* listen are done (Anvil 0.3.0, see [Anvil](anvil/README.md)): harmonics
+  2–10 above a "from" frequency, filled only where the patch lacks them, with
+  the sub level unchanged (problem 19). Open for Ghost: weights that follow the
+  patch's own harmonic slope instead of a fixed 1/k; measuring a new note's
+  harmonics from the lookahead, so its first 60 ms do not count them as
+  missing; a listening check on an 808 over a real phone.
+- **Lathe**: A/B gain snapshots with one automatable Morph parameter. A
+  keyswitch note that selects the drawn shape (EQ switch-ups without
+  automation). A dynamic mode per harmonic.
+- **Temper**: a harmonic split: harmonics 1–2 clean, 3 and up driven. More than
+  one Push band. A bias that changes per cycle from Knurl's cycle clock.
+- **Knurl**: velocity or note selects the pattern. Stereo grit above a split
+  only. Drift (planned for 0.3).
+- **Patina**: Tone guard (done, Patina 0.4.0). MIDI as its pitch source. M/S
+  processing. Threshold, Ratio and Soft/Hard knee from tester feedback (done,
+  Patina 0.5.0). Next, from the same feedback round:
+  - An absolute level gate (dBFS) so quiet passages are never cut, if the
+    tester meant a loudness threshold rather than a prominence threshold.
+  - Narrow rings on dense or noisy material are under-read: a +12 dB ring
+    (Q 25) on noise reads only 3–6 dB above the floor, so it is cut by 1–3 dB.
+    Two causes, measured: the joined-tops envelope lifts the floor to the noise
+    peaks (about 5 dB above the noise mean), and envelope smoothing loses about
+    3 dB on a narrow ring. A floor that follows Sharpness (1/3–2 octaves) was
+    tried and rejected: it lost a resonant lowpass, absorbed broad bumps and cut
+    plain harmonic tones. Better candidates: join tops only across deep gaps
+    (harmonic spacing), or a mean-based floor for noise-like regions.
+  - A finer analysis grid (1024 cells) for narrow rings at high frequencies.
+- **Weld**: delay spread display (done, Weld 0.3.0). A *gentle* fit option
+  that keeps the delay spread under a limit, for plucky layers. Alignment slots
+  per note or per switch-up. The External
+  sender/receiver fallback if FL's sidechain does not arrive.
+- **Crucible**: a heard-onset marker per slice next to the technical cut, set
+  by ear and written to the WAV (problem 21). A switch-up slicer that cuts where the spectrum changes, for
+  legato basses. Optional retune of slices to one root. Reopening saved takes
+  from the `takes` folder in the take list.
+- **Rivet**: more than two sound roles, one per switch-up patch. Its MIDI
+  output as the one note source for the tracked plugins.
+- **Suite**: presets and A/B in `common-ui` for every plugin.
+
 ## Ideas

+### Order
+
+1. Small fixes from the audit. Done: chain-order guide
+   ([Signal chain](chain.md)), Crucible Keep takes. Open: Weld test with delay
+   compensation (in FL), MIDI mode without lookahead (needs an FL check that a
+   latency change at runtime is accepted).
+2. Patina pitch-aware mode. Done as **Tone guard** (Patina 0.4.0): bumps that
+   follow the note are protected, bumps fixed in Hz are cut. Measured first:
+   Patina already cut fixed formants on every note, but it also cut a boosted
+   harmonic as hard (5.7 dB), at a position that moved with the note.
+   Open: MIDI as the pitch source.
+3. Planish (done, released 0.1.0), then Quench and Ballast (both done,
+   released 0.1.0): they fill the mix and master gap.
+   - In parallel, from the research findings, in this order: Weld delay
+     spread (done, Weld 0.3.0); the fatness lane, as the first Assay piece
+     (prototype `scripts/fatness.py`); Anvil Ghost harmonics and Phone listen
+     (done, Anvil 0.3.0); Braze (done, 0.1.0); Anvil Kick lock with offset
+     audition (done, Anvil 0.3.0).
+4. Forge (done, released 0.1.0): Lathe, Temper and Knurl behind one tracker.
+5. Assay, one plugin for the display-only ideas.
+6. Texture plugins (Anneal, Swarf, Etch, Bellows) and the note-keyed sequencer.
+
+Merges: Gauge, Loupe and Drop compare share one analysis core and one display,
+so they become one plugin, **Assay**. The wobble sequencer, Damascus and Chase
+are all "step grid, note selects the pattern", so they become one sequencer.
+
+### Forge — one tracked channel strip (problems 9, 11, latency)
+
+One tracker, one latency, and Lathe, Temper, Knurl and later Anneal as modules
+in an order you choose. Two further reasons from the research findings: one
+modulation source for all modules moves sub, body and top together, which
+binds them into one sound; and coupled macros become possible, for example a
+*Tension* knob that raises roughness (Knurl), inharmonicity and noise (Anneal)
+together at matched loudness, measured by the same descriptors as Loupe. It removes the stacked lookahead, the trackers that
+disagree (Knurl's sub-octave cannot confuse a tracker that reads the input
+before Knurl) and the repeated MIDI routing. The standalone plugins stay.
+Sharing one tracker between separate `.clap` files would need named shared
+memory across DLLs, which is fragile; one strip is simpler.
+
+Built (released 0.1.0, see [Forge](forge/README.md)). Lathe, Temper and Knurl
+became modules (a `Tracked` trait in common-dsp: `ahead`, `event`, `process`);
+each standalone plugin is now its tracker plus its module, Lathe and Temper
+bit-exact against the old engines, Knurl one sample later (its interpolation
+needs one newer sample) and equal within float rounding. In the strip one
+tracker reads the input; a per-sample record of the tracker's events, note state
+and input is replayed to each module, delayed by the latency of the modules in
+front of it. Findings:
+
+- One module alone in Forge matches its standalone plugin sample for sample, in
+  all six orders (tested).
+- Knurl's Double-style pattern (0, −12 dB) in front of Lathe: standalone Lathe
+  after Knurl read the note an octave low in 149 of 149 frames on an A2 saw;
+  Lathe inside Forge read A2 in 149 of 149.
+- Latency 72 ms against 206 ms for the three in a row (48 kHz).
+- Temper's Normalize looks one lookahead ahead; in the strip it reads the strip
+  input, not the modules in front of it. Fine while those change every note's
+  level alike.
+
+Next for Forge: the *Tension* macro over Knurl (and later Anneal) at matched
+loudness; Planish and Braze as modules (both are tracked, and Braze after
+Knurl is the next tracker that hears the sub-octave); a short crossfade when
+the order changes; one shared modulation source (per-note envelope or LFO in
+cycles) that every module can read.
+
+### Braze — tempo-locked beating (problem 20)
+
+Brazing joins two metals with a filler. Braze adds a detuned copy of the bass
+whose beating is in time with the track on every note. With the tracked f0, it
+sets the detune ratio for each note so that a chosen harmonic beats at a
+tempo-synced rate: r = 1 + B/(k·f0), for example an eighth at 140 BPM is
+B = 4.67 Hz. A second mode adds a frequency-shifted copy, so every harmonic
+beats at the same rate. Controls: rate (synced), target harmonic, depth,
+spread across harmonics, mode. It reuses the tracker, and Weld should not
+"fix" this beating: put Weld before Braze.
+
+Built (released 0.1.0, see [Braze](braze/README.md)). The detune is a delay
+line whose delay falls one period per beat cycle and jumps back one period,
+which is seamless on a periodic note, and the delay follows the host's beat
+position, so the peaks land on the grid. Harmonic n then beats at n/k · B: every
+harmonic is on the grid, so the planned spread control was not needed. A Low
+cut (LR4 on the copy, the bass split by the same crossover) keeps the sub out.
+Open: the frequency-shift mode. Mixed with the dry bass, a plain single-sideband
+shift gives every harmonic the same envelope at the same moment, which is
+tremolo; it needs a dispersive allpass on the copy to stagger the harmonics
+before it sounds like movement. Also open: a listening check on a real reese,
+and how Weld reads a layer after Braze.
+
+### Arc — self-FM growl (research spike)
+
+An arc welds with a sustained spark. Arc runs loopback FM (Smyth, DAFx 2026)
+on the tracked note: a time-varying delay line modulated by its own output.
+The closed-form sounding frequency lets Arc retune the carrier, so the growl
+stays in key while feedback sweeps from clean to torn. Needs listening and an
+aliasing check before it becomes a plugin.
+
+### Quench — sub-safe clipper (problem 17)
+
+Quenching hardens hot metal in one fast step. Quench clips only above a split
+frequency and adds the clean sub back with its own headroom, so the master can
+be clipped hard without distorting the low end. Pairs with Anvil's split.
+
+Built (released 0.1.0, see [Quench](quench/README.md)). Design checks, made
+in a prototype before the plugin:
+
+- Splitting and giving the top the instantaneous room, clamp(top, −C − sub,
+  C − sub), is exactly a plain clip of the sum: the error is the same signal.
+  The sub-safe part has to come from somewhere else.
+- Feeding the clip error back through 1 − lowpass diverges: the complement of
+  an LR4 lowpass peaks at 1.5× near the split.
+- What works: clip the top symmetrically at the ceiling minus the sub's held
+  peak (no pumping at the sub's rate, the sum stays under the ceiling), then
+  high-pass the clip error at the split so its products below the split go.
+  Two clip-and-high-pass passes and an oversampled hard clip hold the ceiling.
+  Measured: sub level +0.04 dB against −2.2 dB for a plain clip; low-band
+  products −35 dB against −16 dB. Cost: 0.5–1.2 dB less RMS at the same
+  ceiling.
+- Where it does not help: a top whose fundamental lies within an octave of the
+  split is partly in the sub band (saw at 98 Hz over a 49 Hz sub: about the same
+  as a plain clip).
+- Next ideas: link the channels' sub peak and offer mono below the split
+  (with Gauge); give the top the room on the sub's far side too (asymmetric)
+  with the error still high-passed, and measure whether that wins back the
+  loudness without pumping; a true-peak ceiling.
+
+### Scribe — audio to MIDI (problem 18)
+
+A scribe marks lines on metal. Scribe runs the note tracker on a bass and
+outputs MIDI notes and a `.mid` file. A resample from Crucible then gets its
+notes back, so the other plugins can use MIDI as their source.
+
+### Bevel — mono-safe harmonic widener (problem 5)
+
+Pans harmonics of the note alternately (for example odd left, even right) with
+complementary filters, so the mono sum stays flat. Pairs with Assay.
+
+### Peen — note-start transient shaper
+
+Peening hardens a surface with hammer blows. Attack and sustain shaping on
+every note start, with times counted in cycles, so each switch-up gets the same
+punch on every note. Could become part of Ballast.
+
 ### Ballast — switch-up loudness leveller (problem 2)

 Measures short-term perceived loudness per note or per switch-up against a
@@ -93,6 +571,21 @@ the same loudness without compression changing its character. Earlier working
 name: Hit Leveler. Pairs with Anvil: Anvil levels the sub, Ballast the whole
 patch.

+Built (released 0.1.0, see [Ballast](ballast/README.md)): one gain per part,
+parts from note starts or the host grid (a patch change on the same note is not
+a new note to the tracker), K-weighted loudness of the first 100 ms, Learn for
+the reference. Found while building it:
+
+- A note start from a pitch change comes about 20 ms early, in the gap before
+  the note; a plain mean over the window then reads the part ~0.9 dB quiet.
+  Fixed with 10 ms blocks and a relative gate (−20 dB under the loudest block).
+- The K-weighting filters ring the last part into the next one: a near-silent
+  part after a loud one read −18 LUFS instead of under −60. Fixed by weighting
+  every part from rest.
+- Next ideas: a brightness match next to loudness (problem 2 names both; with
+  Lathe or Patina doing the EQ), a "follow" option for long notes that swell,
+  and switch-up detection from timbre change instead of the grid.
+
 ### Bellows — pitch-tracked resonator

 A comb or Karplus-style resonator tuned to the detected note. It turns noise,
@@ -113,6 +606,15 @@ grids built in. Each MIDI note selects a different pattern, so a switch-up is a
 different note in the piano roll. ShaperBox overlaps, but it has no note-keyed
 patterns. No name yet.

+### Fatness lane (problems 2, 8)
+
+Momentary fatness per 50 ms from Schmedeke's model (see Research findings),
+drawn as one lane next to sub/mid energy, for a patch and a reference. It
+explains why two drops at the same LUFS feel different in weight: a quieter or
+noisier low band lowers the value. Prototype: `scripts/fatness.py` (offline,
+on rendered files). The first piece of Assay. Open: the dB(C) offset, and how
+the lane reads on a single bass patch rather than a full mix.
+
 ### Drop compare (problem 8)

 Loudness-matched A/B of a drop against a reference, with sub, low-mid, mid and
@@ -196,7 +698,21 @@ over time:
 - inharmonicity, which shows how metallic a sound is;
 - brightness relative to the note (harmonic centroid, not centroid in Hz).

+Roughness, inharmonicity and flatness are also the three timbre measures that
+raise judged tension (Farbood and Price 2017), so the same lanes show a build-up
+getting tenser without a note change.
+
 It places every switch-up of a drop as a point on a texture map. Two patches
 that sit on the same point are why a drop sounds repetitive. A reference track
 can be loaded for comparison. Display only, so it is a small build, and it fits
 with Gauge and Drop compare.
+
+### Further leads
+
+- **Creative extrema stretch** for Crucible: Nielsen (DAFx 2026) drives an
+  overlap-add stretch by the spacing of local extrema, a free measure of
+  detail. Cheap and gritty, not transparent; a bass has few extrema per cycle,
+  so the stretch stays close to cycle-synchronous.
+- **Reference to preset:** an offline search over a bounded set of Lathe and
+  Temper parameters that matches a reference switch-up (ST-ITO, TAPE). Large;
+  needs learned audio features.
@@ -1,5 +1,19 @@
 # Knurl changelog

+## 0.3.0
+
+- Add **NOTE** as a pitch source: Knurl follows a note you set, and the audio
+  only starts and stops it. Add Key lock and Follow bends for AUDIO detection.
+- Detection holds its notes: a new note needs a steady pitch for 40 ms, octave
+  jumps need 80 ms down and 200 ms up. Growls, wobbles and formant basses no
+  longer flicker between notes. Follow bends brings back the old fast behaviour.
+- When detection is unsure, Knurl fades its texture out, and the readout shows
+  **?**.
+- The editor opens on a MAIN page. **ADVANCED** in the header adds Edge, the
+  Grit burst's Tone, Position and Length, and Gate.
+- The engine is now a module that also runs inside Forge. The sound is
+  unchanged; the latency is one sample longer.
+
 ## 0.2.0

 - Change the CLAP ID to `io.narl.bass-foundry.knurl`. Hosts see this as a new
@@ -1,7 +1,7 @@
 # Knurl

 Knurl gives every cycle of the note its own level, timing and grit. Current
-version **0.1.0**.
+version **0.3.0**.

 Knurling presses a ridged pattern into metal. Riddim and dubstep basses get their
 character the same way, from surface texture: rattle, growl, fry, grit. Usually
@@ -22,6 +22,10 @@ redistributed packages.

 ## Work with it

+The editor opens on the **MAIN** page with the pattern, Level, Time, Grit, Mix
+and Output. The **ADVANCED** switch in the header adds Edge, the Grit burst's
+Tone, Position and Length, and Gate.
+
 1. Play the bass. The note readout shows what Knurl tracks; the scope overlays
   the last eight cycles of the output, so the texture is visible cycle by cycle.
 2. Choose a **Pattern**. The pattern sets the level of each cycle and repeats:
@@ -50,13 +54,16 @@ note, so identical notes sound identical, which keeps a riddim line tight.

 **Mix** blends with the delayed dry signal; **Output** trims the level.

-### Pitch from MIDI
+### Pitch source

-For basses whose fundamental is unclear (heavy FM, formant or noise patches),
-select **MIDI** and route the bass's MIDI notes to Knurl. In FL Studio, set the
-bass channel's MIDI output port and Knurl's input port to the same number.
-**Gate** sets the input level that counts as a note in AUDIO mode; **Snap to
-semitone** rounds the detected pitch (turn it off for slides).
+**Pitch from** in the header chooses where the note comes from: **AUDIO**
+detects it, **MIDI** follows MIDI notes sent to Knurl, and **NOTE** uses a note
+you set. For heavy FM, formant or noise basses, NOTE with the drop's root is the
+safest choice. Key lock and Follow bends tune the detection. While detection is unsure of the note, Knurl fades its texture out, and the readout shows **?**. See
+[Pitch source](../pitch.md).
+
+**Gate** (ADVANCED page) sets the input level that counts as a note in AUDIO
+mode; **Snap to semitone** rounds the detected pitch (turn it off for slides).

 ## Timing and limits

@@ -72,6 +79,11 @@ the waveform. With a stable pitch that is the same thing. With heavy pitch
 modulation inside a note the pattern follows the tracked pitch, which can lag a
 fast bend. Both channels get the same treatment, so the effect is mono-safe.

+Knurl's patterns put a real sub-octave into the signal. A pitch detector after
+Knurl (Anvil, Lathe or Temper in Audio mode) then reads notes from C2 upwards
+an octave too low. Put Knurl after the other tracked plugins, or use MIDI as
+their source. See [Signal chain](../chain.md).
+
 ## How it works

 A note tracker (shared with Anvil, Lathe and Temper) detects pitch and note
@@ -1,5 +1,18 @@
 # Lathe changelog

+## 0.3.0
+
+- Add **NOTE** as a pitch source: Lathe follows a note you set, and the audio
+  only starts and stops it. Add Key lock and Follow bends for AUDIO detection.
+- Detection holds its notes: a new note needs a steady pitch for 40 ms, octave
+  jumps need 80 ms down and 200 ms up. Growls, wobbles and formant basses no
+  longer flicker between notes. Follow bends brings back the old fast behaviour.
+- When detection is unsure, Lathe passes the audio unchanged instead of cutting
+  a guessed note's harmonics, and the readout shows **?**.
+- The harmonic bars show where harmonics 1, 2, 4, 8, 16 and 32 sit in Hz.
+- The editor opens on a MAIN page. **ADVANCED** in the header adds Harmonics,
+  Smooth, Gate and Snap.
+
 ## 0.2.0

 - Change the CLAP ID to `io.narl.bass-foundry.lathe`. Hosts see this as a new
@@ -1,7 +1,7 @@
 # Lathe

 Lathe is an EQ whose bands sit on the harmonics of the note being played.
-Current version **0.1.0**.
+Current version **0.3.0**.

 A normal EQ works in fixed frequencies. A cut at 130 Hz takes out the 3rd
 harmonic of an F1 bass, the 2nd of a C2, and the fundamental of a C3, so the
@@ -20,8 +20,13 @@ processing. Keep the font license with redistributed packages.

 ## Work with it

+The editor opens on the **MAIN** page with the bars, the macros and Width.
+The **ADVANCED** switch in the header adds Harmonics, Smooth, Gate and Snap.
+
 1. Play the bass. The note readout shows what Lathe tracks; the lower strip of the
   editor shows each harmonic's level going in (grey) and coming out (pink).
+   While a note plays, harmonics 1, 2, 4, 8, 16 and 32 also show where they
+   sit in Hz.
 2. Draw gains on the harmonic bars. Drag across bars to paint a shape;
   Shift-drag for fine steps; double-click a bar to reset it.
 3. Use the macros for the whole series:
@@ -34,7 +39,7 @@ processing. Keep the font license with redistributed packages.
 4. **Width** sets every band's bandwidth as a share of the harmonic spacing. Narrow
   bands touch only the harmonic; wide bands also move its surroundings.

-Other controls:
+Other controls (Harmonics, Smooth, Gate and Snap on the ADVANCED page):

 - **Harmonics** is how many harmonics are shaped (8–32). Higher harmonics pass
  unchanged.
@@ -50,11 +55,13 @@ Other controls:
 The drawn gains are saved with the project but are not automation parameters;
 the macros are.

-### Pitch from MIDI
+### Pitch source

-For basses whose fundamental is unclear (heavy FM, formant or noise patches),
-select **MIDI** and route the bass's MIDI notes to Lathe. In FL Studio, set the
-bass channel's MIDI output port and Lathe's input port to the same number.
+**Pitch from** in the header chooses where the note comes from: **AUDIO**
+detects it, **MIDI** follows MIDI notes sent to Lathe, and **NOTE** uses a note
+you set. For heavy FM, formant or noise basses, NOTE with the drop's root is the
+safest choice. Key lock and Follow bends tune the detection. While detection is unsure of the note, Lathe passes the audio unchanged and the readout shows **?**. See
+[Pitch source](../pitch.md).

 ## Timing and limits

@@ -1,5 +1,32 @@
 # Patina changelog

+## 0.5.0
+
+- Each band now works like a small compressor. Add **Ratio** (1:1 to ∞:1,
+  default ∞:1): low ratios leave small bumps nearly alone and still cut big ones
+  hard. ∞:1 is the old behaviour.
+- Replace Selectivity (%) with **Threshold** (0–18 dB above the local floor,
+  default 3 dB, which equals the old default of 50 %).
+- Add a **Soft/Hard knee** switch. Soft widens the knee from 3 dB to 6 dB;
+  Hard uses a 1 dB knee and half the Attack time.
+- Show the gain curve (bump height in, cut out) under the knobs.
+- Mix and Output move to the slider panel under the plot.
+- Retune the Vocal harshness, Snare ring, Bright synth and Bass line presets
+  with Ratio and more Depth.
+- Breaking: FL Studio projects saved earlier load Threshold, Ratio and Knee at
+  their defaults. Settings files for `patina-render` with `selectivity` still
+  load and convert.
+
+## 0.4.0
+
+- Add **Tone guard** (0–100 %, default 0 %). Patina follows the played note and
+  remembers, over about four seconds, which bumps stay in Hz and which follow the
+  note. Bumps that follow the note (a harmonic the bass is built on) are cut
+  less; resonances fixed in Hz (formant, comb and filter rings) are still cut.
+  At 0 % Patina works exactly as before. The display shows the note and marks
+  the held-back region with a blue strip.
+- Add the **Bass line** preset (Tone guard 80 %, Low 150 Hz).
+
 ## 0.3.0

 - Change the CLAP ID to `io.narl.bass-foundry.patina`. Hosts see this as a new
@@ -1,7 +1,7 @@
 # Patina

 Patina smooths a sound’s rough surface without erasing its character. Formerly
-**Resonance Compressor**; current version **0.2.0**.
+**Resonance Compressor**; current version **0.5.0**.

 A mixing effect that finds harsh, ringing regions as they happen and pulls them
 down, while plain harmonic tone passes. Independently designed in Rust; no claim
@@ -20,18 +20,51 @@ redistributed packages.

 ## Work with it

-Three controls decide what happens:
+Each band works like a small compressor. It compares its level with the local floor
+around it and cuts only the part that sticks out:

- **Depth** is the largest cut, in dB. 0 dB does nothing.
+- **Depth** is the largest cut per band, in dB. 0 dB does nothing.
 - **Sharpness** sets what counts as a resonance. Low values follow broad,
  smooth bumps (honk, boxiness). High values target narrow rings and whistles.
- **Selectivity** sets how far a bump must stand out before it is cut. Low
-  values treat any bump; high values treat only the worst.
+- **Threshold** is how far (dB) a band must rise above its neighbours before it
+  is cut. Low values treat any bump; high values treat only the worst.
+- **Ratio** is how hard a bump above the threshold is cut. At n:1 a bump ends
+  1/n as far above the threshold as it started. Low ratios leave small bumps
+  nearly alone and still cut big ones; ∞:1 flattens every bump to the
+  threshold (this is how Patina worked before 0.5).
+- **Knee**: Soft fades cuts in around the threshold. Hard starts them right at
+  the threshold and uses half the Attack time.

-Start with Depth around 6 dB. Raise Selectivity until only the harsh parts show
-cuts, then use Delta to hear what is removed. Restrict Low/High frequency to keep
-the source’s body out of reach. Attack and Release set how quickly cuts grow and
-recover; Transient guard briefly relaxes cuts on attacks to keep punch.
+The small graph under the knobs shows the result: bump height above the floor
+in, cut out, with the threshold and the Depth limit.
+
+Start with Depth around 6 dB. Raise Threshold until only the harsh parts show
+cuts, then use Delta to hear what is removed. To hit big resonances hard and
+leave small ones alone, raise Depth to 12–20 dB and set Ratio to 2:1–4:1.
+Restrict Low/High frequency to keep the source’s body out of reach. Attack and
+Release set how quickly cuts grow and recover; Transient guard briefly relaxes
+cuts on attacks to keep punch.
+
+### Tone guard for bass lines
+
+On a bass line, a bump can mean two things. A resonance fixed in Hz (a formant,
+a comb or filter ring) stays at the same frequency on every note: that is what
+Patina should cut. A bump that follows the note (a harmonic the patch is built
+on, or a Lathe boost) moves with every note: cutting it changes the patch
+differently on each note.
+
+**Tone guard** tells them apart. Patina detects the played note (30–500 Hz)
+and remembers, over about four seconds, how high each bump was in Hz and how
+high it was relative to the note. A bump that has stayed with the note more
+than in Hz gets less cut; at 100 % none. A resonance fixed in Hz is cut as
+before. It needs a few different notes before it can decide: on one held note
+both look the same and Patina cuts as normal. The **NOTE** readout shows what
+Patina follows, and a blue strip on top of the plot shows where cuts are held
+back. Start from the **Bass line** preset. At 0 % Tone guard is off.
+
+Measured on a saw line F1–F2 with Low at 150 Hz: a +12 dB boost on harmonic 6
+is cut by 5.8 dB without Tone guard and by 0.4 dB at 100 %; a formant at 1.5 kHz
+is cut by 5.8 dB either way.

 Double-click the plot to add one of four focus points. Drag a point up to cut
 more in that region, down to protect it. Wheel changes its width. Range handles
@@ -40,7 +73,7 @@ on the plot drag the processing limits.
 On the plot, the grey fill is the measured input. The bright line is what the
 detector hears (its smoothed spectral envelope); the dim line is what it expects
 there. Accent-coloured cuts appear where the bright line rises above the dim one
-by more than Selectivity allows. The blue curve is the focus/protect shape.
+by more than Threshold allows. The blue curve is the focus/protect shape.

 Delta plays delayed dry minus wet before output trim. Use it to inspect changes,
 then return to normal monitoring to decide whether the music improved.
@@ -62,8 +95,9 @@ window size persist; Delta does not.
 4. The reference is a robust local straight-line fit over 2–3 octaves: spectral
   tilt is expected, bumps cannot raise their own reference, and empty regions
   (below a fundamental, beyond a filter cutoff) are ignored.
-5. Envelope minus reference, above the Selectivity threshold, becomes the cut,
-   limited by Depth, smoothed with Attack/Release, and linked across stereo.
+5. Envelope minus reference is the band's height above its floor. Above
+   Threshold it becomes a cut through the Knee and Ratio curve, limited by
+   Depth, smoothed with Attack/Release, and linked across stereo.

 ## Timing and limits

@@ -76,7 +110,8 @@ The engine uses complex RustFFT with supplied scratch buffers, WOLA reconstructi
 the envelope/reference detector above, bounded soft-knee cuts, and temporal
 smoothing. Original bin phases are retained. This is not a minimum-phase filter
 bank, a live monitoring effect, a limiter, or an automatic separation of tone and
-unwanted resonance. No external sidechain, Learn, M/S, or pitch detector in v0.1.
+unwanted resonance. No external sidechain, Learn or M/S. The pitch detector
+serves Tone guard only.

 ## Build and offline evaluation

@@ -120,7 +155,9 @@ The CLAP ID is now `io.narl.bass-foundry.patina` (earlier builds used
 `io.storyboard.resonance-compressor`). Hosts treat Patina as a new plugin, so
 add it again in projects saved with an earlier build. Version 0.2 replaced
 Amount, Sensitivity, Max cut, Neighborhood, Cut width, and Knee with Depth,
-Sharpness, and Selectivity. Delete the old plugin file, place `Patina.clap`, and
+Sharpness, and Selectivity; version 0.5 replaced Selectivity with Threshold
+(dB), Ratio and Knee, so projects saved earlier load Threshold at its default.
+Delete the old plugin file, place `Patina.clap`, and
 rescan FL Studio.

 Source is grouped into `plugins/patina/{core,ui,render,plugin}`. See
@@ -0,0 +1,62 @@
+# Pitch source in the tracked plugins
+
+Anvil, Lathe, Temper, Knurl, Planish, Braze and Forge follow the note the bass
+plays. **Pitch from** in each header says where that note comes from.
+
+- **AUDIO** detects the note from the audio. This is the default.
+- **MIDI** takes the notes from MIDI input. In FL Studio, set the bass channel's
+  MIDI output port and the effect's input port to the same number.
+- **NOTE** uses a note you set, for example F1. The audio only starts and stops
+  notes; nothing is detected. Most riddim drops sit on one or two roots, so this
+  is the safest choice for growls, FM basses and anything detection struggles
+  with. Click the note button next to NOTE to pick the note and its octave.
+
+## When detection is unsure
+
+Real basses are often not one clear note: FM growls, formant sweeps, detuned
+reeses, layers and noise. Detection therefore stays put:
+
+- A new note needs a steady pitch for 40 ms. A jump down an octave needs 80 ms
+  and a jump up an octave 200 ms, because a misread octave is the commonest
+  error.
+- Inside a note, the tuning only moves when the pitch drifts more than a quarter
+  of a semitone for good.
+- When the pitch keeps reading differently from the note (about 40 ms of
+  disagreeing reads, or 400 ms without any clear read), the note turns
+  **unsure**. The NOTE readout then shows **?**.
+
+While the note is unsure, a plugin never acts on a guess:
+
+| Plugin | While unsure |
+| --- | --- |
+| Anvil | Plays your original sub instead of the sine (Enhance: adds nothing) |
+| Lathe | Passes the audio unchanged |
+| Knurl | Fades its texture out |
+| Temper, Planish, Braze | Keep the tuning of the last sure note |
+| Forge | Each module as above |
+
+## Key lock and Follow bends
+
+With AUDIO selected, the button next to the switch opens two options:
+
+- **Key lock** lets detection pick only notes of a key: **Minor**, **Major**,
+  or **Root only** (any octave of the root, so detection only picks the
+  octave). Pick the root below. A drop in F minor with Key lock on F minor can
+  no longer read an F♯.
+- **Follow bends** retunes on every bend and vibrato and switches notes after
+  10 ms, as the plugins did before. It follows slides and 808 glides closely,
+  but it flickers on growls. Leave it off unless the bass is clean and bends a
+  lot.
+
+## Measuring detection on your own stems
+
+`cargo run -p common-dsp --release --example tracker_report` scores the
+detection on a set of synthetic stems (growls, wobble, reese, formant bass, 808
+slide, layered drop, noise riser). Pass WAV files to score real stems:
+
+```text
+cargo run -p common-dsp --release --example tracker_report -- --note F1 drop.wav
+```
+
+It prints note starts per second, the share of time with a wrong sure note, and
+the share of time detection was unsure.
@@ -0,0 +1,27 @@
+# Planish changelog
+
+## 0.2.0
+
+- Add **NOTE** as a pitch source: Planish follows a note you set, and the audio
+  only starts and stops it. Add Key lock and Follow bends for AUDIO detection.
+- Detection holds its notes: a new note needs a steady pitch for 40 ms, octave
+  jumps need 80 ms down and 200 ms up. Growls, wobbles and formant basses no
+  longer flicker between notes. Follow bends brings back the old fast behaviour.
+- When detection is unsure, the band edges hold on the last sure note, and the
+  readout shows **?**. On a new note the edges slide over 6 ms instead of
+  jumping.
+- The editor opens on a MAIN page. **ADVANCED** in the header adds the band
+  gains, Smooth, Gate and Snap.
+
+## 0.1.0
+
+- Introduce Planish, upward and downward compression in four bands whose edges
+  are harmonic numbers of the played note.
+- Band edges set by harmonic (Low 1–8, Mid 2–16, High 3–48), with splits
+  Classic, Sub + body, Tight and Wide top, or dragged on the harmonic ruler.
+- Depth, Drive, Upward, Downward, Time and a gain per band.
+- Band level measured over one period of the note, so heavy compression does
+  not ripple at the fundamental.
+- Detect pitch and note starts from the audio with about 67 ms of latency, or
+  follow MIDI notes sent to the effect.
+- Editor shows the bands on a harmonic ruler and each band's level and gain.
@@ -0,0 +1,105 @@
+# Planish
+
+Planish is upward and downward compression (OTT) in four bands whose edges are
+harmonic numbers of the played note. Current version **0.2.0**.
+
+Planishing hammers a metal surface smooth and even. OTT does the same to a bass:
+it pushes loud bands down and lifts quiet ones, and it is on almost every riddim
+patch. A normal OTT splits the bands at fixed frequencies, though. A split at
+88 Hz and 2.5 kHz puts harmonic 2 of F1 in the low band but harmonic 2 of C2 in
+the mid band, so the same setting squashes different harmonics on every note.
+Planish moves its band edges with the note: with the default split, band 1 is
+the fundamental, band 2 harmonics 2–4, band 3 harmonics 5–16 and band 4
+everything above, on F1 as on G2.
+
+![Planish](assets/editor.png)
+
+## Install on Windows
+
+Copy `Planish.clap` into `C:\Program Files\Common Files\CLAP\`. In FL Studio
+2024.1 or newer, open Options → Manage plugins, enable Verify plugins, and Find
+installed plugins. Load Planish in a mixer slot of the bass. Keep the font
+license with redistributed packages.
+
+## Work with it
+
+The editor opens on the **MAIN** page with the split, Drive, Depth, Upward,
+Downward, Time and Output. The **ADVANCED** switch in the header adds the band
+gains, Smooth, Gate and Snap.
+
+1. Play the bass. The note readout shows what Planish tracks. The ruler at the
+   top shows harmonics 1–64 and the four bands; the columns below show each
+   band's level (steel) and gain (pink for a cut, blue for a lift).
+2. Choose a split, or drag an edge on the ruler:
+   - **Classic** (1, 2–4, 5–16, 17+, the default): fundamental on its own.
+   - **Sub + body** (1–2, 3–6, 7–24, 25+): the octave stays with the sub.
+   - **Tight** (1, 2, 3–8, 9+): close control of the first harmonics.
+   - **Wide top** (1, 2–3, 4–32, 33+): one big mid band, the top is fizz only.
+3. Set the amount:
+   - **Depth** blends each band with its compressed copy. 0 % is a clean sum
+     of the bands; the default is 50 %.
+   - **Drive** moves the band levels against the thresholds: more drive, more
+     squash. It does not change the level by itself.
+   - **Upward** and **Downward** scale the two directions. Downward pushes a
+     band above −30 dB down at about 20:1; Upward lifts a band below −42 dB at
+     about 4:1, by at most 24 dB.
+   - **Time** scales every attack and release. Lower bands are slower: at
+     100 %, attack is 30, 15, 8 and 4 ms and release 200, 160, 120 and 90 ms
+     from band 1 to band 4.
+4. On the ADVANCED page, **Band 1–4** set each band's gain after its compressor. Like the
+   compression, they are scaled by Depth.
+
+**Output** trims the level. **Bypass** crossfades to the delayed dry signal.
+
+### Pitch source
+
+**Pitch from** in the header chooses where the note comes from: **AUDIO**
+detects it, **MIDI** follows MIDI notes sent to Planish, and **NOTE** uses a note
+you set. For heavy FM, formant or noise basses, NOTE with the drop's root is the
+safest choice. Key lock and Follow bends tune the detection. While detection is unsure of the note, the band edges hold on the last sure note and the readout shows **?**. See
+[Pitch source](../pitch.md).
+
+**Gate** (ADVANCED page) sets the input level that counts as a note in AUDIO
+mode. **Snap to semitone** rounds the detected pitch; it is off by default,
+because the level is measured over one period of the pitch in use, and a
+detuned patch fits its real period better.
+
+## Measured
+
+- At Depth 0 the bands sum flat: sines from 35 Hz to 12 kHz come out within
+  0.05 dB.
+- The same setting changes the same harmonics on every note. At Depth 100 %
+  on a saw bass, harmonic 1 is cut by 13.6 dB on F1, C2 and G2; harmonics 1–12
+  differ by less than 0.2 dB between the three notes.
+- No ripple at the fundamental. A 40 Hz sine at Drive +12 dB and Time 10 % gets
+  no harmonics above −110 dB.
+
+## Timing and limits
+
+Planish delays the audio by about 67 ms of pitch-detection lookahead and
+reports it to the host for delay compensation, so the edges are on the new note
+when its attack leaves the plugin. Pitch range is 30–500 Hz, one note at a time.
+Before the first note the edges sit on 55 Hz; between notes they hold the last
+note. On a new note the edges slide to it over 6 ms, so the crossovers do not
+click.
+
+An edge is a slope, not a wall. The crossovers are 24 dB per octave, so the
+harmonics next to an edge partly reach the next band, by the same amount on
+every note. Both channels get the same gain per band, so the stereo image does
+not move. Quiet signals below about −84 dB are not lifted, so noise floors and
+tails stay down.
+
+Planish detects the pitch like Lathe and Temper. Put it before Knurl, or use
+MIDI: see [Signal chain](../chain.md).
+
+## How it works
+
+A note tracker (shared with Anvil, Lathe, Temper and Knurl) detects pitch and
+note starts ahead of the delayed audio. Three Linkwitz–Riley crossovers split
+the signal at √(k(k+1)) × f0, halfway in log frequency between harmonic k and
+k+1, and allpasses keep the lower bands in phase with the upper ones, so the
+bands sum to an allpass. The crossovers retune every 16 samples and glide with
+**Smooth** on bends. Each band's level is the RMS over exactly one period of
+the note, so a steady note gives a steady level and the gain does not wobble
+at f0. The level goes through attack and release smoothing, then a static
+curve with an upward and a downward threshold sets the gain.
@@ -0,0 +1,16 @@
+# Quench changelog
+
+## 0.1.0
+
+- Introduce Quench, a clipper that clips the top and lets the sub pass clean.
+- A Linkwitz–Riley split at **Split** (40–300 Hz). The top is clipped at the
+  ceiling minus the sub's held peak; **Hold** sets how long that peak holds.
+- What the clip removes is high-passed at Split, so its products stay out of
+  the low band. Two correction passes and an oversampled hard clip hold the
+  ceiling; a safety clip catches the downsampler's ringing.
+- **Drive**, **Ceiling**, **Soft** (knee of the top's clip), **Bypass**.
+- Listen to **Quench**, a **Plain** clipper at the same settings, or the
+  **Delta** that Quench takes away. Not saved.
+- Editor: how much the low band changed for Quench and for a plain clip, how
+  far the top is clipped, the sub's peak and the room it leaves, and a scope.
+- 4× oversampling; 37 samples of latency.
@@ -0,0 +1,104 @@
+# Quench
+
+Quench clips the top of the mix as hard as you like and lets the sub pass clean.
+Current version **0.1.0**.
+
+Riddim and dubstep masters are clipped hard. A plain clipper clips the sum of
+the sub and everything above it. Near the sub's peaks only one side of the top
+gets clipped, so the clipping takes energy out at the sub's rate: the sub loses
+level, and the low end fills with products that were not in the mix. Quench
+splits the signal at a frequency you set, never clips the sub, and clips only
+the top, in the room the sub leaves under the ceiling.
+
+![Quench](assets/editor.png)
+
+## Install on Windows
+
+Copy `Quench.clap` into `C:\Program Files\Common Files\CLAP\`. In FL Studio
+2024.1 or newer, open Options → Manage plugins, enable Verify plugins, and Find
+installed plugins. Load Quench last on the master or on the bass bus. Keep the
+font license with redistributed packages.
+
+## Work with it
+
+1. Put Quench where you would put a clipper: last on the master, or last on
+   the bass bus. Before a true-peak limiter is fine.
+2. Set **Ceiling**, the highest output peak.
+3. Set **Split** above the highest sub note, or at Anvil's Split when Anvil
+   makes the sub. Everything below Split passes without clipping.
+4. Raise **Drive** until the top clips as hard as you want. The panel shows
+   how far the top is clipped.
+5. Press **PLAIN** to hear a plain clipper at the same settings, then
+   **QUENCH** again. **DELTA** plays only what Quench takes away. The listen
+   choice is not saved and goes back to QUENCH when the editor closes.
+
+The panel shows:
+
+- **Low end changed by**: how much the band below Split differs from the
+  input, against the sub's level, for Quench and for a plain clip of the same
+  signal. Lower is cleaner. It reads "—" when no sub plays.
+- **Top clipped by**: how far the top's loudest peak went past its room.
+- **Sub peak · room left**: the sub's peak after Drive and the room it leaves
+  the top under the ceiling.
+- The scope: the output (grey), the sub band (blue), and the sub plus or minus
+  the top's room (thin lines). The output stays between the thin lines.
+
+Other controls:
+
+- **Hold** keeps the room the sub's peak needs for this long. With a hold
+  longer than half a period of the lowest note (17 ms at 30 Hz), the top's
+  clip level stays steady through the sub's cycle and the top does not pump
+  with the sub. Shorter holds give the top a little more room between sub
+  peaks, and that room then changes at the sub's rate.
+- **Soft** bends the top's clip: 0 % is a hard clip, 100 % a soft curve from
+  the start. The ceiling stays a hard limit.
+- **Bypass** crossfades to the input, delayed by the latency.
+
+When the sub alone reaches the ceiling, the top has no room left. The panel
+then warns: lower Drive or the sub. A safety clip still holds the ceiling, and
+that clip does cut the sub.
+
+### How it works
+
+A Linkwitz–Riley crossover splits the signal at Split. The sub passes. The top
+is clipped symmetrically at the ceiling minus the sub's held peak, so the sum
+of sub and top never goes over the ceiling.
+
+Clipping the top also makes products below Split, for example difference
+tones between its partials. Quench high-passes what the clip removed at Split,
+so those products do not reach the low band. High-passing lets a few peaks
+overshoot. Two correction passes clip those again and high-pass the correction,
+and a final hard clip at the ceiling takes the small rest. All of this runs at
+4× oversampling. A safety clip after the downsampler catches the filters'
+ringing; it reads "idle" or a few hundredths of a dB.
+
+Measured on a 50 Hz sub at −10.5 dBFS under a top of five unrelated partials
+peaking about 6 dB over the ceiling:
+
+| | Sub level | Low-band products |
+| --- | --- | --- |
+| Plain clip | −2.2 dB | −16 dB |
+| Quench | +0.04 dB | −35 dB |
+
+Low-band products are everything below 110 Hz except the sub, against the
+sub's level.
+
+Quench pays for this in loudness. The top gets the room on the sub's quieter
+side only, so at the same ceiling Quench measured 0.5–1.2 dB lower in RMS
+than a plain clip. Add Drive to make up for it.
+
+## Timing and limits
+
+Latency is the oversampling filters: 37 samples (0.8 ms at 48 kHz), reported
+to the host for delay compensation.
+
+The split is a slope, not a wall. A top whose own fundamental lies near
+Split, for example a distorted patch an octave above a 49 Hz sub, is partly in
+the sub band. That part passes unclipped and takes up room, and Quench helps
+less there: on a saw top at 98 Hz it changed the low end about as much as a
+plain clip. Keep the top's lowest partial at least an octave above Split.
+
+Quench keeps the ceiling on sample peaks. True peaks between samples can
+still go a little over it: put a true-peak limiter after Quench if the master
+needs one. Each channel is clipped on its own; Quench does not link the
+channels or turn the sub to mono.
@@ -8,13 +8,18 @@ workflows are in `.gitea/workflows/`. A plugin's version is the `version` in
 | Plugin | Latest tag | Windows download |
 | --- | --- | --- |
 | Rivet | `rivet-v0.5.0` | `rivet-windows-x86_64-0.5.0.zip` |
-| Patina | `patina-v0.3.0` | `patina-windows-x86_64-0.3.0.zip` |
-| Anvil | `anvil-v0.2.0` | `anvil-windows-x86_64-0.2.0.zip` |
-| Crucible | `crucible-v0.2.0` | `crucible-windows-x86_64-0.2.0.zip` |
-| Lathe | `lathe-v0.2.0` | `lathe-windows-x86_64-0.2.0.zip` |
-| Temper | `temper-v0.2.0` | `temper-windows-x86_64-0.2.0.zip` |
-| Weld | `weld-v0.2.0` | `weld-windows-x86_64-0.2.0.zip` |
-| Knurl | `knurl-v0.2.0` | `knurl-windows-x86_64-0.2.0.zip` |
+| Patina | `patina-v0.5.0` | `patina-windows-x86_64-0.5.0.zip` |
+| Anvil | `anvil-v0.4.0` | `anvil-windows-x86_64-0.4.0.zip` |
+| Crucible | `crucible-v0.4.0` | `crucible-windows-x86_64-0.4.0.zip` |
+| Lathe | `lathe-v0.3.0` | `lathe-windows-x86_64-0.3.0.zip` |
+| Temper | `temper-v0.3.0` | `temper-windows-x86_64-0.3.0.zip` |
+| Weld | `weld-v0.4.0` | `weld-windows-x86_64-0.4.0.zip` |
+| Knurl | `knurl-v0.3.0` | `knurl-windows-x86_64-0.3.0.zip` |
+| Planish | `planish-v0.2.0` | `planish-windows-x86_64-0.2.0.zip` |
+| Braze | `braze-v0.2.0` | `braze-windows-x86_64-0.2.0.zip` |
+| Quench | `quench-v0.1.0` | `quench-windows-x86_64-0.1.0.zip` |
+| Ballast | `ballast-v0.2.0` | `ballast-windows-x86_64-0.2.0.zip` |
+| Forge | `forge-v0.2.0` | `forge-windows-x86_64-0.2.0.zip` |

 ## Make a release

@@ -1,7 +1,7 @@
 # Rivet

 Rivet joins short motifs into connected musical phrases, like a fastener joining
-individual pieces. Formerly **Motif Storyboard**; current version **0.4.0**.
+individual pieces. Formerly **Motif Storyboard**; current version **0.5.0**.


 A Rust composition companion for a producer developing their own melodic ideas.
@@ -1,5 +1,17 @@
 # Temper changelog

+## 0.3.0
+
+- Add **NOTE** as a pitch source: Temper follows a note you set, and the audio
+  only starts and stops it. Add Key lock and Follow bends for AUDIO detection.
+- Detection holds its notes: a new note needs a steady pitch for 40 ms, octave
+  jumps need 80 ms down and 200 ms up. Growls, wobbles and formant basses no
+  longer flicker between notes. Follow bends brings back the old fast behaviour.
+- When detection is unsure, Temper keeps the tuning of the last sure note, and
+  the readout shows **?**.
+- The editor opens on a MAIN page. **ADVANCED** in the header adds Push at,
+  Floor, Bright, Normalize and Gate.
+
 ## 0.2.0

 - Change the CLAP ID to `io.narl.bass-foundry.temper`. Hosts see this as a new
@@ -1,6 +1,6 @@
 # Temper

-Temper is a distortion that drives every note the same. Current version **0.1.0**.
+Temper is a distortion that drives every note the same. Current version **0.3.0**.

 A distortion with a fixed tone filter acts differently on each note: a lowpass
 at 2 kHz lets through 45 harmonics of an F1 but only 22 of an F2, and
@@ -20,6 +20,10 @@ with redistributed packages.

 ## Work with it

+The editor opens on the **MAIN** page with Curve, Drive, Bias, Push, Mix and
+Output. The **ADVANCED** switch in the header adds Push at, Floor, Bright,
+Normalize and Gate.
+
 1. Choose a **Curve**:
   - **Soft**: tanh, smooth and rounded.
   - **Hard**: clipping with a narrow knee, dense and square-like.
@@ -47,11 +51,13 @@ Other controls:
 - **Gate** is the input level that counts as a note.
 - **Mix** blends with the delayed dry signal; **Output** trims the level.

-### Pitch from MIDI
+### Pitch source

-Select **MIDI** and route the bass's MIDI notes to Temper when detection
-struggles. In FL Studio, set the bass channel's MIDI output port and Temper's
-input port to the same number.
+**Pitch from** in the header chooses where the note comes from: **AUDIO**
+detects it, **MIDI** follows MIDI notes sent to Temper, and **NOTE** uses a note
+you set. For heavy FM, formant or noise basses, NOTE with the drop's root is the
+safest choice. Key lock and Follow bends tune the detection. While detection is unsure of the note, Temper keeps the tuning of the last sure note and the readout shows **?**. See
+[Pitch source](../pitch.md).

 ## Timing and limits

@@ -1,5 +1,19 @@
 # Weld changelog

+## 0.4.0
+
+- The editor opens on a MAIN page with Recovered, the band plot, Mode,
+  Response, Output and the time offset. **ADVANCED** in the header adds the
+  phase plot, Sections, Low, High and Gate. Sound and saved settings do not
+  change.
+
+## 0.3.0
+
+- Show the **delay spread**: how much the alignment's group delay changes
+  between 500 Hz and 4 kHz, where listeners hear it best. Above 0.64 ms (the
+  threshold Liski et al. 2021 measured on clicks) a note suggests comparing
+  attacks in SUM and SUM DRY. Display only; the sound does not change.
+
 ## 0.2.0

 - Change the CLAP ID to `io.narl.bass-foundry.weld`. Hosts see this as a new
@@ -1,7 +1,7 @@
 # Weld

 Weld fuses two bass layers so they add up instead of cancelling. Current version
-**0.1.0**.
+**0.4.0**.

 Bass patches are layered: a sub, one or more mid growls, a top. Where the layers
 overlap in the mids, they partly cancel. The causes are a polarity difference, a
@@ -37,6 +37,10 @@ plugins. Keep the font license with redistributed packages.

 ## Work with it

+The editor opens on the **MAIN** page: Recovered, the band plot, Mode,
+Response, Output and the time offset. The **ADVANCED** switch in the header adds
+the phase plot, Sections, Low, High and Gate.
+
 1. Leave **Mode** on **FOLLOW** and play the part where both layers sound. After
   a second or two, Weld shows its alignment: polarity, and the allpass sections
   with their frequency and Q.
@@ -47,9 +51,14 @@ plugins. Keep the font license with redistributed packages.
   - The upper plot shows each band against a perfectly aligned sum (0 dB). Red
     is what the unprocessed sum loses to cancellation; pink is the part Weld
     wins back. The white line is the level with Weld.
-   - The lower plot shows the phase of this layer against the other one, before
+   - On the ADVANCED page, the lower plot shows the phase of this layer against the other one, before
     (grey) and after (pink), and Weld's own phase curve (blue). After alignment
     the pink line sits near 0°.
+   - **Delay spread** under the sections is how much Weld's delay changes
+     between 500 Hz and 4 kHz. On clicks, listeners hear about 0.6 ms of change
+     there (Liski et al. 2021); sustained bass hides much more, and common fits
+     reach 0.8–1 ms. Above that threshold Weld adds a note: on a plucky layer,
+     compare the attacks in SUM and SUM DRY. Fewer sections usually spread less.
 3. Compare by ear: mute the other layer's own route to the master, set
   **Listen** to **SUM**, then to **SUM DRY**. Set Listen back to **LAYER** and
   unmute the route for the mix.
@@ -4,10 +4,27 @@
 //! The audio path is delayed by a fixed lookahead. Detection runs on the undelayed input, so
 //! a note's pitch is known before its delayed attack leaves the plugin, and the sine starts
 //! exactly on that attack.
+//!
+//! Ghost harmonics add the sub's own harmonics above a chosen frequency, so the note
+//! reads on speakers without sub. The band above the split is measured per harmonic and
+//! only the harmonics the patch lacks are filled: a harmonic the patch already has would
+//! meet the added one at an unrelated phase and could cancel.
+//!
+//! The sine only plays while the note is sure. While tracking is unsure, the original sub
+//! comes back in its place (Replace) or the added sine fades out (Enhance), so a wrong guess
+//! never plays a wrong sub note.
+//!
+//! Kick lock reads the kick from the sidechain. Hits are found on the undelayed sidechain,
+//! so with the lookahead each hit ducks the sub exactly when the delayed kick plays, and
+//! restarts the sub's phase at the kick plus an offset, also before the kick. The audition
+//! plays each offset of a sweep for a few kicks and measures how kick and sub sum in the
+//! low band for each one; what sums loudest is not always what sounds like one hit.
 mod settings;
-use common_dsp::tracker::{NoteEvent, Tracker, TrackerConfig};
-use common_dsp::{coefficient, db_to_gain, hz_to_midi, midi_to_hz, Crossover};
-pub use settings::{Settings, Source};
+use common_dsp::meter::HarmonicMeter;
+use common_dsp::svf::{Svf, SvfCoef};
+use common_dsp::tracker::{Fallback, NoteEvent, Tracker, TrackerConfig};
+use common_dsp::{coefficient, db_to_gain, hz_to_midi, midi_to_hz, Biquad, Crossover};
+pub use settings::{Mode, Settings, Source, KICK_OFFSET_MAX};
 use std::f32::consts::TAU;

 /// Detectable fundamental range. The lowest sets the lookahead (two periods).
@@ -17,11 +34,46 @@ pub const SCOPE: usize = 256;
 const ATTACK_MS: f32 = 2.;
 const RELEASE_MS: f32 = 15.;
 const CROSSFADE_MS: f32 = 3.;
+/// Crossfade between the sine and the original sub when tracking turns unsure or sure.
+const TRUST_MS: f32 = 15.;
+/// Highest Ghost harmonic. Harmonic 10 of a 30 Hz sub is 300 Hz.
+pub const GHOST_TOP: usize = 10;
+/// Ghost harmonics shown and generated: 2..=GHOST_TOP.
+pub const GHOST_COUNT: usize = GHOST_TOP - 1;
+/// Measurement window per note. Resolves harmonics of fundamentals down to about 35 Hz.
+const GHOST_WINDOW_MS: f32 = 60.;
+/// Harmonics fade in over this many octaves above the Ghost edge, so a gliding note
+/// does not switch them on with a step.
+const GHOST_RAMP_OCT: f32 = 0.5;
+/// Offsets the audition steps through, in ms.
+pub const AUDITION: [f32; 13] = [
+    -30., -25., -20., -15., -10., -5., 0., 5., 10., 15., 20., 25., 30.,
+];
+/// Kicks each audition offset plays for.
+pub const AUDITION_HITS: u32 = 4;
+/// A kick is a rise of the fast sidechain envelope this far above the slow one...
+const KICK_RISE: f32 = 2.8;
+/// ...above this level (−45 dBFS)...
+const KICK_FLOOR: f32 = 0.0056;
+/// ...at least this long after the previous kick.
+const KICK_HOLD_MS: f32 = 60.;
+/// Kick and sub are compared below this frequency, over this long after each hit.
+const KICK_LOW_HZ: f32 = 150.;
+const SUM_MS: f32 = 60.;
+const DUCK_ATTACK_MS: f32 = 1.;
+const PENDING: usize = 16;
+/// Small speaker listen: a phone-like band, summed to mono.
+pub const PHONE_LOW: f32 = 400.;
+pub const PHONE_HIGH: f32 = 7000.;

 #[derive(Clone, Copy, Debug, Default)]
 pub struct Monitor {
-    /// Hear only the generated sub.
+    /// Hear only the generated sub and Ghost harmonics.
    pub solo: bool,
+    /// Hear the output through a phone-like speaker band, in mono.
+    pub phone: bool,
+    /// Step the kick offset through `AUDITION`, `AUDITION_HITS` kicks each.
+    pub audition: bool,
 }

 #[derive(Clone, Copy, Debug)]
@@ -30,8 +82,25 @@ pub struct AnalyzerFrame {
    pub hz: f32,
    /// MIDI note of the current sub, rounded.
    pub note: Option<u8>,
+    /// Tracking is unsure: the original sub plays instead of the sine.
+    pub neutral: bool,
    pub low_db: f32,
    pub sub_db: f32,
+    /// Harmonics 2..=GHOST_TOP of the current note, peak dB relative to the sub: what the
+    /// patch carries above the split, and what Ghost adds. −120 when absent.
+    pub patch_harmonics: [f32; GHOST_COUNT],
+    pub ghost_harmonics: [f32; GHOST_COUNT],
+    /// Lowest frequency Ghost fills, after the split.
+    pub ghost_edge: f32,
+    /// Kicks found in the sidechain since the plugin started.
+    pub kick_hits: u32,
+    /// Kick plus sub against kick and sub apart, low band, dB, after the last hit. +3 is a
+    /// full sum of equal levels, 0 unrelated, below 0 they cancel. NaN before a hit.
+    pub kick_sum_db: f32,
+    /// Offset the sub restarted with on the latest kick, in ms.
+    pub kick_offset: f32,
+    /// Measured sum per audition offset, dB; NaN where not measured yet.
+    pub audition_sums: [f32; AUDITION.len()],
    /// Original low band and new sub, triggered on a rising zero crossing of the sub.
    pub scope_low: [f32; SCOPE],
    pub scope_sub: [f32; SCOPE],
@@ -45,8 +114,16 @@ impl Default for AnalyzerFrame {
        Self {
            hz: 0.,
            note: None,
+            neutral: false,
            low_db: -120.,
            sub_db: -120.,
+            patch_harmonics: [-120.; GHOST_COUNT],
+            ghost_harmonics: [-120.; GHOST_COUNT],
+            ghost_edge: 300.,
+            kick_hits: 0,
+            kick_sum_db: f32::NAN,
+            kick_offset: 0.,
+            audition_sums: [f32::NAN; AUDITION.len()],
            scope_low: [0.; SCOPE],
            scope_sub: [0.; SCOPE],
            scope_ms: 60.,
@@ -72,6 +149,8 @@ struct Synth {
    old: Voice,
    old_gain: f32,
    note_peak: f32,
+    /// Set when a note starts or changes pitch; the Ghost measurement starts over.
+    fresh: bool,
 }
 impl Synth {
    fn event(&mut self, s: &Settings, e: NoteEvent) {
@@ -111,6 +190,112 @@ impl Synth {
            self.voice.hz = hz;
        }
        self.note_peak = 0.;
+        self.fresh = true;
+    }
+    /// Restarts a sounding sub at the start phase, keeping its pitch.
+    fn kick(&mut self, s: &Settings) {
+        let v = self.voice;
+        if v.amp <= 1e-4 || v.releasing {
+            return;
+        }
+        self.old = v;
+        self.old_gain = 1.;
+        self.voice = Voice {
+            phase: s.phase / 360.,
+            amp: 0.,
+            ..v
+        };
+    }
+}
+
+#[derive(Clone, Copy, Debug, Default)]
+struct Pending {
+    /// Output-time sample.
+    at: u64,
+    /// Restart the sub (true) or duck it and start measuring (false).
+    restart: bool,
+    offset: f32,
+    /// Audition offset index this hit belongs to.
+    slot: Option<usize>,
+}
+
+/// Kick detection, scheduling, ducking and the sum measurement.
+struct Kick {
+    clock: u64,
+    fast: f32,
+    slow: f32,
+    fast_coef: f32,
+    slow_coef: f32,
+    hold: usize,
+    pending: [Option<Pending>; PENDING],
+    delay: Vec<f32>,
+    delay_at: usize,
+    low: Biquad,
+    duck: f32,
+    rising: bool,
+    attack: f32,
+    measure: usize,
+    measure_slot: Option<usize>,
+    energy: [f32; 3],
+    hits: u32,
+    sum_db: f32,
+    offset: f32,
+    auditioning: bool,
+    slot: usize,
+    slot_hits: u32,
+    sums: [f32; AUDITION.len()],
+    counts: [u32; AUDITION.len()],
+}
+impl Kick {
+    fn new(rate: f32, latency: usize) -> Self {
+        Self {
+            clock: 0,
+            fast: 0.,
+            slow: 0.,
+            fast_coef: coefficient(rate, 0.5),
+            slow_coef: coefficient(rate, 30.),
+            hold: 0,
+            pending: [None; PENDING],
+            delay: vec![0.; latency + 1],
+            delay_at: 0,
+            low: Biquad::lowpass(rate, KICK_LOW_HZ, std::f32::consts::FRAC_1_SQRT_2),
+            duck: 0.,
+            rising: false,
+            attack: coefficient(rate, DUCK_ATTACK_MS / 3.),
+            measure: 0,
+            measure_slot: None,
+            energy: [0.; 3],
+            hits: 0,
+            sum_db: f32::NAN,
+            offset: 0.,
+            auditioning: false,
+            slot: 0,
+            slot_hits: 0,
+            sums: [f32::NAN; AUDITION.len()],
+            counts: [0; AUDITION.len()],
+        }
+    }
+    fn reset(&mut self) {
+        self.fast = 0.;
+        self.slow = 0.;
+        self.hold = 0;
+        self.pending = [None; PENDING];
+        self.delay.fill(0.);
+        self.low.reset();
+        self.duck = 0.;
+        self.rising = false;
+        self.measure = 0;
+        self.measure_slot = None;
+        self.sum_db = f32::NAN;
+        self.slot = 0;
+        self.slot_hits = 0;
+        self.sums = [f32::NAN; AUDITION.len()];
+        self.counts = [0; AUDITION.len()];
+    }
+    fn schedule(&mut self, p: Pending) {
+        if let Some(free) = self.pending.iter_mut().find(|p| p.is_none()) {
+            *free = Some(p);
+        }
    }
 }

@@ -132,6 +317,11 @@ pub struct Engine {
    keep: f32,
    output: f32,
    bypass: f32,
+    fallback: Fallback,
+    neutral: bool,
+    /// 1 while the sine plays, 0 while the original sub stands in for it.
+    trust: f32,
+    trust_coef: f32,
    meter_coef: f32,
    low_power: f32,
    sub_power: f32,
@@ -140,6 +330,14 @@ pub struct Engine {
    scope_at: usize,
    scope_stride: usize,
    scope_count: usize,
+    meter: HarmonicMeter,
+    /// Linear peak of the patch's harmonic k (index k − 2) above the split, this note.
+    patch: [f32; GHOST_COUNT],
+    /// Smoothed Ghost gain per harmonic, relative to the sub's peak.
+    fill: [f32; GHOST_COUNT],
+    phone_coefs: [SvfCoef; 3],
+    phone: [Svf; 3],
+    kick: Kick,
 }

 impl Engine {
@@ -171,6 +369,10 @@ impl Engine {
            keep: 0.,
            output: 1.,
            bypass: 0.,
+            fallback: Fallback::default(),
+            neutral: false,
+            trust: 1.,
+            trust_coef: coefficient(rate, TRUST_MS / 3.),
            meter_coef: coefficient(rate, 150.),
            low_power: 0.,
            sub_power: 0.,
@@ -179,6 +381,17 @@ impl Engine {
            scope_at: 0,
            scope_stride: ((rate * 0.06) / SCOPE as f32).round().max(1.) as usize,
            scope_count: 0,
+            meter: HarmonicMeter::new(rate, GHOST_WINDOW_MS),
+            patch: [0.; GHOST_COUNT],
+            fill: [0.; GHOST_COUNT],
+            phone_coefs: [
+                // Fourth-order Butterworth high-pass, second-order low-pass.
+                SvfCoef::highpass(rate, PHONE_LOW, 0.541),
+                SvfCoef::highpass(rate, PHONE_LOW, 1.307),
+                SvfCoef::lowpass(rate, PHONE_HIGH.min(0.45 * rate), 0.707),
+            ],
+            phone: [Svf::default(); 3],
+            kick: Kick::new(rate, latency),
        };
        e.set_settings(settings)?;
        Ok(e)
@@ -202,7 +415,7 @@ impl Engine {
        }
        if self
            .tracker
-            .set(s.source == Source::Midi, s.gate, s.glide > 0.)
+            .set(s.pitch.source(s.source.mode(), s.gate, s.glide > 0.))
        {
            self.synth.voice.releasing = true;
        }
@@ -221,11 +434,57 @@ impl Engine {
        }
        self.tracker.reset();
        self.synth = Synth::default();
+        self.fallback.reset();
+        self.neutral = false;
+        self.trust = 1.;
        self.low_env = 0.;
        self.low_power = 0.;
        self.sub_power = 0.;
        self.scope_low = [0.; 2 * SCOPE];
        self.scope_sub = [0.; 2 * SCOPE];
+        self.meter.reset();
+        self.patch = [0.; GHOST_COUNT];
+        self.fill = [0.; GHOST_COUNT];
+        for f in &mut self.phone {
+            f.reset();
+        }
+        self.kick.reset();
+    }
+    /// Lowest frequency Ghost fills.
+    fn ghost_edge(&self) -> f32 {
+        self.settings.ghost_from.max(self.settings.split)
+    }
+    /// Moves each Ghost gain toward what the patch lacks at the current note.
+    fn update_fill(&mut self) {
+        let s = &self.settings;
+        let v = self.synth.voice;
+        let amount = s.ghost * 0.01;
+        let edge = self.ghost_edge();
+        let sub = self.level.max(1e-6);
+        for (i, fill) in self.fill.iter_mut().enumerate() {
+            let k = (i + 2) as f32;
+            let f = k * v.hz;
+            let target = if amount > 0. && v.hz > 0. && f < 0.45 * self.rate {
+                let ramp = ((f / edge).log2() / GHOST_RAMP_OCT).clamp(0., 1.);
+                // A 1/k slope, like a saw; at 100 % harmonic k sits at 2/k of the sub.
+                let want = amount * 2. / k * ramp;
+                (want - self.patch[i] / sub).max(0.)
+            } else {
+                0.
+            };
+            *fill += (target - *fill) * self.smooth;
+        }
+    }
+    /// Ghost harmonics for a voice at `phase`, without the voice's amplitude.
+    #[inline]
+    fn ghost(&self, phase: f32) -> f32 {
+        let mut out = 0.;
+        for (i, &g) in self.fill.iter().enumerate() {
+            if g > 1e-5 {
+                out += g * (TAU * ((i + 2) as f32 * phase).fract()).sin();
+            }
+        }
+        out
    }
    /// MIDI note start at the current input sample. Used when the source is MIDI.
    pub fn note_on(&mut self, note: u8) {
@@ -243,7 +502,8 @@ impl Engine {
        let k = 1. + 6. * drive;
        (k * x).tanh() / k.tanh()
    }
-    fn oscillator(&mut self) -> f32 {
+    /// The shaped sub and the Ghost harmonics, before level and dynamics.
+    fn oscillator(&mut self) -> (f32, f32) {
        let attack = 1. / (self.rate * ATTACK_MS * 0.001);
        let release = 1. / (self.rate * RELEASE_MS * 0.001);
        let v = &mut self.synth.voice;
@@ -253,21 +513,145 @@ impl Engine {
            (v.amp + attack).min(1.)
        };
        v.hz += (v.target - v.hz) * self.glide;
-        let mut out = 0.;
+        let (mut out, mut ghost) = (0., 0.);
+        let v = self.synth.voice;
        if v.amp > 0. {
            out += (TAU * v.phase).sin() * v.amp;
-            v.phase = (v.phase + v.hz / self.rate).fract();
+            ghost += self.ghost(v.phase) * v.amp;
+            self.synth.voice.phase = (v.phase + v.hz / self.rate).fract();
        }
-        let s = &mut self.synth;
+        let s = self.synth;
        if s.old_gain > 0. {
-            let o = &mut s.old;
+            let o = s.old;
            out += (TAU * o.phase).sin() * o.amp * s.old_gain;
-            o.phase = (o.phase + o.hz / self.rate).fract();
+            ghost += self.ghost(o.phase) * o.amp * s.old_gain;
+            let s = &mut self.synth;
+            s.old.phase = (o.phase + o.hz / self.rate).fract();
            s.old_gain = (s.old_gain - 1. / (self.rate * CROSSFADE_MS * 0.001)).max(0.);
        }
-        self.shape(out)
+        (self.shape(out), ghost)
    }
+    /// One sample without a sidechain.
    pub fn process_sample(&mut self, x: [f32; 2], monitor: Monitor) -> [f32; 2] {
+        self.process_with_kick(x, 0., monitor)
+    }
+    /// Finds kicks in the undelayed sidechain and schedules their duck and restart.
+    fn detect_kick(&mut self, side: f32, audition: bool) {
+        let rate = self.rate;
+        let s = self.settings;
+        let k = &mut self.kick;
+        if audition != k.auditioning {
+            k.auditioning = audition;
+            k.slot = 0;
+            k.slot_hits = 0;
+            k.sums = [f32::NAN; AUDITION.len()];
+            k.counts = [0; AUDITION.len()];
+        }
+        let level = side.abs();
+        k.fast += (level - k.fast) * k.fast_coef;
+        k.slow += (level - k.slow) * k.slow_coef;
+        k.hold = k.hold.saturating_sub(1);
+        if !s.kick_lock || k.hold > 0 || k.fast < KICK_FLOOR || k.fast < KICK_RISE * k.slow {
+            return;
+        }
+        k.hold = (rate * KICK_HOLD_MS * 0.001) as usize;
+        let (offset, slot) = if audition {
+            let slot = k.slot;
+            k.slot_hits += 1;
+            if k.slot_hits >= AUDITION_HITS {
+                k.slot_hits = 0;
+                k.slot = (k.slot + 1) % AUDITION.len();
+            }
+            (AUDITION[slot], Some(slot))
+        } else {
+            (s.kick_offset, None)
+        };
+        // The delayed kick leaves the plugin `latency` samples from now.
+        let at = k.clock + self.latency as u64;
+        let shift = (offset * 0.001 * rate).round() as i64;
+        let duck = Pending {
+            at,
+            restart: false,
+            offset,
+            slot,
+        };
+        k.schedule(duck);
+        k.schedule(Pending {
+            at: (at as i64 + shift).max(0) as u64,
+            restart: true,
+            ..duck
+        });
+    }
+    /// Runs the kick events due at this output sample. Returns the duck gain for the sub.
+    fn kick_events(&mut self) -> f32 {
+        let s = self.settings;
+        let clock = self.kick.clock;
+        for i in 0..PENDING {
+            let Some(p) = self.kick.pending[i] else {
+                continue;
+            };
+            if p.at > clock {
+                continue;
+            }
+            self.kick.pending[i] = None;
+            if p.restart {
+                self.synth.kick(&s);
+                self.kick.offset = p.offset;
+            } else {
+                let k = &mut self.kick;
+                k.hits += 1;
+                k.rising = true;
+                k.measure = (self.rate * SUM_MS * 0.001) as usize;
+                k.measure_slot = p.slot;
+                k.energy = [0.; 3];
+            }
+        }
+        let k = &mut self.kick;
+        if k.rising {
+            k.duck += (1. - k.duck) * k.attack;
+            if k.duck > 0.98 {
+                k.rising = false;
+            }
+        } else {
+            k.duck -= k.duck * coefficient(self.rate, s.kick_release / 3.);
+        }
+        if !s.kick_lock {
+            k.duck = 0.;
+        }
+        1. - (1. - db_to_gain(-s.kick_duck)) * k.duck
+    }
+    /// Adds one sample of the delayed kick's and the sub's low band to the sum measurement.
+    fn measure_kick(&mut self, kick: f32, sub: f32) {
+        let k = &mut self.kick;
+        if k.measure == 0 {
+            return;
+        }
+        k.energy[0] += (kick + sub) * (kick + sub);
+        k.energy[1] += kick * kick;
+        k.energy[2] += sub * sub;
+        k.measure -= 1;
+        if k.measure > 0 {
+            return;
+        }
+        let apart = k.energy[1] + k.energy[2];
+        if apart < 1e-9 {
+            return;
+        }
+        k.sum_db = 10. * (k.energy[0] / apart).max(1e-6).log10();
+        if let Some(slot) = k.measure_slot {
+            let n = k.counts[slot] as f32;
+            let old = if n > 0. { k.sums[slot] } else { 0. };
+            k.sums[slot] = (old * n + k.sum_db) / (n + 1.);
+            k.counts[slot] += 1;
+        }
+    }
+    /// One sample with the kick's sidechain (mono) for Kick lock.
+    pub fn process_with_kick(&mut self, x: [f32; 2], kick: f32, monitor: Monitor) -> [f32; 2] {
+        self.detect_kick(kick, monitor.audition);
+        let len = self.kick.delay.len();
+        self.kick.delay[self.kick.delay_at] = kick;
+        self.kick.delay_at = (self.kick.delay_at + 1) % len;
+        let kick_late = self.kick.delay[self.kick.delay_at];
        let mono = if self.channels == 2 {
            0.5 * (x[0] + x[1])
        } else {
@@ -275,6 +659,7 @@ impl Engine {
        };
        let (synth, settings) = (&mut self.synth, &self.settings);
        self.tracker.process(mono, |e| synth.event(settings, e));
+        self.neutral = self.fallback.neutral(self.tracker.state());
        let len = self.delay.len();
        self.delay[self.delay_at] = x;
        self.delay_at = (self.delay_at + 1) % len;
@@ -288,6 +673,19 @@ impl Engine {
            (l0, h0)
        };
        let low = 0.5 * (l0 + l1);
+        if std::mem::take(&mut self.synth.fresh) {
+            // A new note: measure its harmonics from its first sample. Until the first
+            // window completes they count as missing.
+            self.meter.reset();
+            self.patch = [0.; GHOST_COUNT];
+        }
+        let v = self.synth.voice;
+        let hz = if v.amp > 0. && !v.releasing { v.hz } else { 0. };
+        if self.meter.push(0.5 * (h0 + h1), hz) && self.meter.hz() > 0. {
+            for (p, db) in self.patch.iter_mut().zip(&self.meter.levels()[1..]) {
+                *p = if *db > -119. { db_to_gain(*db) } else { 0. };
+            }
+        }
        self.low_env += (low * low - self.low_env) * self.env_coef;
        let env = self.low_env.sqrt();
        if !self.synth.voice.releasing {
@@ -304,21 +702,37 @@ impl Engine {
        self.keep += (s.keep * 0.01 - self.keep) * self.smooth;
        self.output += (db_to_gain(s.output) - self.output) * self.smooth;
        self.bypass += (f32::from(s.bypass) - self.bypass) * self.smooth;
-        let sub = self.oscillator() * self.level * shape;
+        let duck = self.kick_events();
+        self.update_fill();
+        let (sub, ghost) = self.oscillator();
+        self.trust += (f32::from(!self.neutral) - self.trust) * self.trust_coef;
+        let gain = self.level * shape * duck * self.trust;
+        let sub = sub * gain;
+        let generated = sub + ghost * gain;
+        if self.settings.kick_lock {
+            let kick_low = self.kick.low.process(kick_late);
+            self.measure_kick(kick_low, sub);
+        }
+        self.kick.clock += 1;
        self.low_power += (low * low - self.low_power) * self.meter_coef;
        self.sub_power += (sub * sub - self.sub_power) * self.meter_coef;
        self.scope_count += 1;
        if self.scope_count >= self.scope_stride {
            self.scope_count = 0;
            self.scope_low[self.scope_at] = low;
-            self.scope_sub[self.scope_at] = sub;
+            self.scope_sub[self.scope_at] = generated;
            self.scope_at = (self.scope_at + 1) % (2 * SCOPE);
        }
+        // Replace keeps `keep` of the original, and all of it while the sine is out.
+        let keep = match s.mode {
+            Mode::Replace => self.keep + (1. - self.keep) * (1. - self.trust),
+            Mode::Enhance => 1.,
+        };
        let wet = |l: f32, h: f32| {
            if monitor.solo {
-                sub
+                generated
            } else {
-                h + self.keep * l + sub
+                h + keep * l + generated
            }
        };
        let w = [wet(l0, h0), wet(l1, h1)];
@@ -326,6 +740,17 @@ impl Engine {
        for c in 0..self.channels {
            out[c] = (w[c] * self.output) * (1. - self.bypass) + y[c] * self.bypass;
        }
+        if monitor.phone {
+            let mut m = if self.channels == 2 {
+                0.5 * (out[0] + out[1])
+            } else {
+                out[0]
+            };
+            for (f, c) in self.phone.iter_mut().zip(&self.phone_coefs) {
+                m = f.process(c, m);
+            }
+            out = [m, if self.channels == 2 { m } else { 0. }];
+        }
        out
    }
    pub fn take_analyzer(&self) -> AnalyzerFrame {
@@ -335,10 +760,28 @@ impl Engine {
            low_db: 10. * self.low_power.max(1e-12).log10() + 3.01,
            sub_db: 10. * self.sub_power.max(1e-12).log10() + 3.01,
            scope_ms: (self.scope_stride * SCOPE) as f32 / self.rate * 1000.,
+            ghost_edge: self.ghost_edge(),
+            kick_hits: self.kick.hits,
+            kick_sum_db: self.kick.sum_db,
+            kick_offset: self.kick.offset,
+            audition_sums: self.kick.sums,
+            neutral: self.neutral,
            ..AnalyzerFrame::default()
        };
+        let sub = self.level.max(1e-6);
+        let rel = |g: f32| {
+            if g > 1e-6 {
+                20. * (g / sub).log10()
+            } else {
+                -120.
+            }
+        };
+        for i in 0..GHOST_COUNT {
+            f.patch_harmonics[i] = rel(self.patch[i]);
+            f.ghost_harmonics[i] = rel(self.fill[i] * sub);
+        }
        let v = self.synth.voice;
-        if v.amp > 0. && !v.releasing {
+        if v.amp > 0. && !v.releasing && !self.neutral {
            f.hz = v.hz;
            f.note = Some(hz_to_midi(v.hz).round().clamp(0., 127.) as u8);
        }
@@ -1,4 +1,5 @@
 //! Host-independent controls. Levels in dB, times in milliseconds, frequencies in Hz.
+use common_dsp::tracker::{Pitch, PitchMode};
 use serde::{Deserialize, Serialize};

 #[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
@@ -8,12 +9,45 @@ pub enum Source {
    Audio,
    /// Notes come from MIDI note input; the audio only supplies the band above the split.
    Midi,
+    /// Note starts are detected, the pitch is the set note: nothing is guessed.
+    Note,
+}
+impl Source {
+    pub fn mode(self) -> PitchMode {
+        match self {
+            Source::Audio => PitchMode::Audio,
+            Source::Midi => PitchMode::Midi,
+            Source::Note => PitchMode::Note,
+        }
+    }
+    pub fn from_mode(mode: PitchMode) -> Self {
+        match mode {
+            PitchMode::Audio => Source::Audio,
+            PitchMode::Midi => Source::Midi,
+            PitchMode::Note => Source::Note,
+        }
+    }
+}
+
+/// What happens to the original sub.
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
+pub enum Mode {
+    /// The band below the split is replaced by the clean sine (plus Keep of the original).
+    #[default]
+    Replace,
+    /// The original sub stays, and the sine is added under it for weight.
+    Enhance,
 }

 #[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq)]
 #[serde(deny_unknown_fields)]
 pub struct Settings {
    pub source: Source,
+    /// Note mode's note, the key lock and Follow bends.
+    #[serde(default)]
+    pub pitch: Pitch,
+    #[serde(default)]
+    pub mode: Mode,
    /// Peak level of the new sub in dBFS, the same for every note.
    pub level: f32,
    /// Crossover frequency: below it the original sub is replaced.
@@ -22,6 +56,13 @@ pub struct Settings {
    pub dynamics: f32,
    /// Soft saturation of the sine, adding upper harmonics for small speakers.
    pub drive: f32,
+    /// Ghost harmonics: adds the sub's harmonics 2–10 above `ghost_from`, so small
+    /// speakers hear the note. Only harmonics the patch lacks are filled. 0 is off.
+    #[serde(default)]
+    pub ghost: f32,
+    /// Lowest frequency Ghost harmonics reach down to, in Hz (never below `split`).
+    #[serde(default = "default_ghost_from")]
+    pub ghost_from: f32,
    pub octave: i32,
    /// Pitch slide time between overlapping notes.
    pub glide: f32,
@@ -37,15 +78,45 @@ pub struct Settings {
    /// Round detected pitch to the nearest semitone.
    pub snap: bool,
    pub bypass: bool,
+    /// Kick lock: on each kick in the sidechain, duck the sub and restart its phase.
+    #[serde(default)]
+    pub kick_lock: bool,
+    /// How far the sub dips on each kick, in dB.
+    #[serde(default = "default_kick_duck")]
+    pub kick_duck: f32,
+    /// Time for the sub to come back after a kick, in ms.
+    #[serde(default = "default_kick_release")]
+    pub kick_release: f32,
+    /// When the sub restarts against the kick's start, in ms. Negative: before the kick.
+    #[serde(default)]
+    pub kick_offset: f32,
+}
+const GHOST_FROM: f32 = 300.;
+const KICK_DUCK: f32 = 6.;
+const KICK_RELEASE: f32 = 80.;
+/// Range of the kick offset, in ms either side of the kick.
+pub const KICK_OFFSET_MAX: f32 = 30.;
+fn default_kick_duck() -> f32 {
+    KICK_DUCK
+}
+fn default_kick_release() -> f32 {
+    KICK_RELEASE
+}
+fn default_ghost_from() -> f32 {
+    GHOST_FROM
 }
 impl Default for Settings {
    fn default() -> Self {
        Self {
            source: Source::Audio,
+            pitch: Pitch::default(),
+            mode: Mode::Replace,
            level: -9.,
            split: 90.,
            dynamics: 0.,
            drive: 0.,
+            ghost: 0.,
+            ghost_from: GHOST_FROM,
            octave: 0,
            glide: 0.,
            phase: 0.,
@@ -55,21 +126,31 @@ impl Default for Settings {
            retrigger: true,
            snap: true,
            bypass: false,
+            kick_lock: false,
+            kick_duck: KICK_DUCK,
+            kick_release: KICK_RELEASE,
+            kick_offset: 0.,
        }
    }
 }
 impl Settings {
    pub fn validate(&self) -> Result<(), &'static str> {
+        self.pitch.validate()?;
        let finite = [
            self.level,
            self.split,
            self.dynamics,
            self.drive,
+            self.ghost,
+            self.ghost_from,
            self.glide,
            self.phase,
            self.gate,
            self.keep,
            self.output,
+            self.kick_duck,
+            self.kick_release,
+            self.kick_offset,
        ]
        .iter()
        .all(|v| v.is_finite());
@@ -80,12 +161,17 @@ impl Settings {
            && (40.0..=200.).contains(&self.split)
            && (0.0..=100.).contains(&self.dynamics)
            && (0.0..=100.).contains(&self.drive)
+            && (0.0..=100.).contains(&self.ghost)
+            && (150.0..=600.).contains(&self.ghost_from)
            && (-2..=1).contains(&self.octave)
            && (0.0..=200.).contains(&self.glide)
            && (0.0..=360.).contains(&self.phase)
            && (-60.0..=-20.).contains(&self.gate)
            && (0.0..=100.).contains(&self.keep)
-            && (-12.0..=12.).contains(&self.output);
+            && (-12.0..=12.).contains(&self.output)
+            && (0.0..=24.).contains(&self.kick_duck)
+            && (10.0..=300.).contains(&self.kick_release)
+            && (-KICK_OFFSET_MAX..=KICK_OFFSET_MAX).contains(&self.kick_offset);
        if ok {
            Ok(())
        } else {
@@ -1,4 +1,4 @@
-use anvil_core::{Engine, Monitor, Settings, Source};
+use anvil_core::{Engine, Mode, Monitor, Settings, Source};
 use common_dsp::Saw;

 const RATE: f32 = 48000.;
@@ -19,7 +19,15 @@ fn notes(list: &[(f32, f32, f32, f32)], total: f32) -> Vec<f32> {
 }
 fn render(e: &mut Engine, x: &[f32], solo: bool) -> Vec<f32> {
    x.iter()
-        .map(|&s| e.process_sample([s, s], Monitor { solo })[0])
+        .map(|&s| {
+            e.process_sample(
+                [s, s],
+                Monitor {
+                    solo,
+                    ..Monitor::default()
+                },
+            )[0]
+        })
        .collect()
 }
 fn rms(x: &[f32]) -> f32 {
@@ -135,7 +143,15 @@ fn midi_notes_set_pitch_and_are_delayed_by_the_latency() {
        if i == seconds(0.6) {
            e.note_off(33);
        }
-        y.push(e.process_sample([0.; 2], Monitor { solo: true })[0]);
+        y.push(
+            e.process_sample(
+                [0.; 2],
+                Monitor {
+                    solo: true,
+                    ..Monitor::default()
+                },
+            )[0],
+        );
    }
    assert!(y[..1000 + l].iter().all(|v| *v == 0.));
    assert!(y[1000 + l + 50].abs() > 0.);
@@ -211,3 +227,334 @@ fn settings_are_validated_and_serialise() {
    assert!(Engine::new(1000., 2).is_err());
    assert!(Engine::new(48000., 3).is_err());
 }
+
+/// Peak amplitude of the component at `hz`, over a window of whole cycles.
+fn amplitude(x: &[f32], hz: f32) -> f32 {
+    let w = std::f32::consts::TAU * hz / RATE;
+    let (re, im) = x.iter().enumerate().fold((0., 0.), |(re, im), (n, v)| {
+        (re + v * (w * n as f32).cos(), im - v * (w * n as f32).sin())
+    });
+    2. * (re * re + im * im).sqrt() / x.len() as f32
+}
+/// Sines (Hz, peak) from 0.1 s to `total` − 0.1 s, with 1 ms fades.
+fn tones(list: &[(f32, f32)], total: f32) -> Vec<f32> {
+    let n = (total * RATE) as usize;
+    let (a, b, fade) = (seconds(0.1), n - seconds(0.1), seconds(0.001));
+    (0..n)
+        .map(|i| {
+            if i < a || i >= b {
+                return 0.;
+            }
+            let edge = ((i - a).min(b - 1 - i) as f32 / fade as f32).min(1.);
+            let t = (i - a) as f32 / RATE;
+            edge * list
+                .iter()
+                .map(|&(hz, amp)| amp * (std::f32::consts::TAU * hz * t).sin())
+                .sum::<f32>()
+        })
+        .collect()
+}
+fn ghost(amount: f32) -> Settings {
+    Settings {
+        ghost: amount,
+        ghost_from: 300.,
+        ..Settings::default()
+    }
+}
+
+#[test]
+fn ghost_fills_the_harmonics_a_clean_sub_lacks() {
+    let (mut e, l) = engine(ghost(100.));
+    let x = tones(&[(55., 0.5)], 1.);
+    let y = render(&mut e, &x, true);
+    // 0.2 s holds exactly 11 cycles of 55 Hz.
+    let w = &y[seconds(0.5) + l..seconds(0.7) + l];
+    let sub = amplitude(w, 55.);
+    assert!((db(sub) + 9.).abs() < 0.5, "{}", db(sub));
+    for k in 2..=5 {
+        // Below Ghost from: nothing added, so the sub stays a clean sine there.
+        let a = amplitude(w, 55. * k as f32);
+        assert!(db(a / sub) < -60., "harmonic {k}: {}", db(a / sub));
+    }
+    for k in 8..=10 {
+        let a = amplitude(w, 55. * k as f32);
+        let expect = 20. * (2. / k as f32).log10();
+        assert!(
+            (db(a / sub) - expect).abs() < 1.,
+            "harmonic {k}: {}",
+            db(a / sub)
+        );
+    }
+    // Harmonic 6 (330 Hz) sits in the fade above 300 Hz: present, but quieter.
+    let six = db(amplitude(w, 330.) / sub);
+    assert!(six < 20. * (2f32 / 6.).log10() - 3. && six > -40., "{six}");
+}
+
+#[test]
+fn ghost_leaves_harmonics_the_patch_already_has() {
+    let (mut e, l) = engine(ghost(100.));
+    // The patch carries its 8th harmonic (440 Hz) louder than Ghost would add it.
+    let x = tones(&[(55., 0.5), (440., 0.2)], 1.);
+    let y = render(&mut e, &x, false);
+    let w = &y[seconds(0.5) + l..seconds(0.7) + l];
+    let eighth = amplitude(w, 440.);
+    assert!((db(eighth) - db(0.2)).abs() < 0.5, "{}", db(eighth));
+    // The 9th is missing from the patch, so Ghost fills it.
+    let ninth = amplitude(w, 495.) / amplitude(w, 55.);
+    assert!(
+        (db(ninth) - 20. * (2f32 / 9.).log10()).abs() < 1.,
+        "{}",
+        db(ninth)
+    );
+}
+
+#[test]
+fn ghost_off_adds_nothing_and_phone_listen_drops_the_sub() {
+    let x = tones(&[(55., 0.5)], 1.);
+    let (mut e, l) = engine(ghost(0.));
+    let y = render(&mut e, &x, true);
+    let w = &y[seconds(0.5) + l..seconds(0.7) + l];
+    for k in 2..=10 {
+        assert!(amplitude(w, 55. * k as f32) < 1e-4, "harmonic {k}");
+    }
+    let phone = |amount: f32| {
+        let (mut e, l) = engine(ghost(amount));
+        let y: Vec<f32> = x
+            .iter()
+            .map(|&s| {
+                e.process_sample(
+                    [s, s],
+                    Monitor {
+                        solo: true,
+                        phone: true,
+                        audition: false,
+                    },
+                )[0]
+            })
+            .collect();
+        rms(&y[seconds(0.5) + l..seconds(0.7) + l])
+    };
+    // A clean 55 Hz sub all but vanishes on a phone; Ghost makes the note heard.
+    let (plain, ghosted) = (phone(0.), phone(100.));
+    assert!(db(plain) < -50., "{}", db(plain));
+    assert!(
+        db(ghosted) - db(plain) > 25.,
+        "{} vs {}",
+        db(ghosted),
+        db(plain)
+    );
+}
+
+/// A kick-like burst: a 55 Hz sine starting at phase 0 with a 60 ms decay, at each time.
+fn kicks(times: &[f32], total: f32) -> Vec<f32> {
+    let mut k = vec![0.; seconds(total)];
+    for &t in times {
+        for i in 0..seconds(0.2) {
+            let n = seconds(t) + i;
+            if n < k.len() {
+                let t = i as f32 / RATE;
+                k[n] += 0.8 * (std::f32::consts::TAU * 55. * t).sin() * (-t / 0.06).exp();
+            }
+        }
+    }
+    k
+}
+fn render_kick(e: &mut Engine, x: &[f32], k: &[f32], monitor: Monitor) -> Vec<f32> {
+    x.iter()
+        .zip(k)
+        .map(|(&s, &k)| e.process_with_kick([s, s], k, monitor)[0])
+        .collect()
+}
+/// Normalised correlation of `y[a..b]` with a sine of `hz` at phase 0 at sample `zero`.
+fn sine_match(y: &[f32], a: usize, b: usize, hz: f32, zero: f32) -> f32 {
+    let w = std::f32::consts::TAU * hz / RATE;
+    let (mut xy, mut xx, mut yy) = (0., 0., 0.);
+    for (i, &v) in y.iter().enumerate().take(b).skip(a) {
+        let r = (w * (i as f32 - zero)).sin();
+        xy += v * r;
+        xx += r * r;
+        yy += v * v;
+    }
+    xy / (xx * yy).sqrt()
+}
+const SOLO: Monitor = Monitor {
+    solo: true,
+    phone: false,
+    audition: false,
+};
+fn kick_lock(offset: f32) -> Settings {
+    Settings {
+        kick_lock: true,
+        kick_offset: offset,
+        ..Settings::default()
+    }
+}
+
+#[test]
+fn a_kick_restarts_the_sub_at_the_start_phase_and_ducks_it() {
+    // A bass note that started off the kick: before the hit, the sub runs at its own phase.
+    let x = tones(&[(55., 0.5)], 1.4);
+    let k = kicks(&[0.613], 1.4);
+    let (mut e, l) = engine(kick_lock(0.));
+    let y = render_kick(&mut e, &x, &k, SOLO);
+    let hit = seconds(0.613) + l;
+    let after = sine_match(
+        &y,
+        hit + seconds(0.004),
+        hit + seconds(0.04),
+        55.,
+        hit as f32,
+    );
+    assert!(after > 0.99, "{after}");
+    let before = rms(&y[hit - seconds(0.1)..hit - seconds(0.01)]);
+    let ducked = rms(&y[hit + seconds(0.004)..hit + seconds(0.022)]);
+    let back = rms(&y[hit + seconds(0.4)..hit + seconds(0.5)]);
+    assert!(
+        db(before) - db(ducked) > 2.,
+        "{} vs {}",
+        db(before),
+        db(ducked)
+    );
+    assert!(
+        (db(back) - db(before)).abs() < 0.3,
+        "{} vs {}",
+        db(back),
+        db(before)
+    );
+    assert_eq!(e.take_analyzer().kick_hits, 1);
+}
+
+#[test]
+fn the_offset_restarts_the_sub_before_or_after_the_kick() {
+    let x = tones(&[(55., 0.5)], 1.2);
+    let k = kicks(&[0.613], 1.2);
+    for offset in [-10., 7.] {
+        // No duck: only the phase is checked here.
+        let (mut e, l) = engine(Settings {
+            kick_duck: 0.,
+            ..kick_lock(offset)
+        });
+        let y = render_kick(&mut e, &x, &k, SOLO);
+        let start = (seconds(0.613) + l) as f32 + offset * 0.001 * RATE;
+        let a = start as usize + seconds(0.004);
+        let m = sine_match(&y, a, a + seconds(0.03), 55., start);
+        assert!(m > 0.99, "{offset}: {m}");
+    }
+}
+
+#[test]
+fn without_kick_lock_the_sidechain_changes_nothing() {
+    let x = tones(&[(55., 0.5)], 1.);
+    let k = kicks(&[0.3, 0.6], 1.);
+    let (mut a, _) = engine(Settings::default());
+    let (mut b, _) = engine(Settings::default());
+    let with = render_kick(&mut a, &x, &k, SOLO);
+    let without = render(&mut b, &x, true);
+    assert_eq!(with, without);
+}
+
+#[test]
+fn the_audition_finds_where_kick_and_sub_sum() {
+    use anvil_core::{AUDITION, AUDITION_HITS};
+    let hits = AUDITION.len() * AUDITION_HITS as usize;
+    let total = 0.5 + hits as f32 * 0.2 + 0.4;
+    let x = tones(&[(55., 0.5)], total);
+    let times: Vec<f32> = (0..hits).map(|i| 0.5 + i as f32 * 0.2).collect();
+    let k = kicks(&times, total);
+    let (mut e, _) = engine(kick_lock(0.));
+    let monitor = Monitor {
+        audition: true,
+        ..SOLO
+    };
+    render_kick(&mut e, &x, &k, monitor);
+    let f = e.take_analyzer();
+    assert_eq!(f.kick_hits as usize, hits);
+    let sums = f.audition_sums;
+    assert!(sums.iter().all(|v| v.is_finite()), "{sums:?}");
+    // The kick is a 55 Hz burst at phase 0, like the sub: they sum fully at 0 ms and
+    // cancel half a period (9 ms) away.
+    let best = (0..sums.len())
+        .max_by(|&a, &b| sums[a].total_cmp(&sums[b]))
+        .unwrap();
+    assert_eq!(AUDITION[best], 0., "{sums:?}");
+    let zero = sums[6];
+    assert!(zero > 2., "{zero}");
+    for i in [4, 8] {
+        assert!(
+            zero - sums[i] > 4.,
+            "{} ms: {} vs {zero}",
+            AUDITION[i],
+            sums[i]
+        );
+    }
+}
+
+#[test]
+fn unsure_tracking_brings_back_the_original_sub() {
+    let (mut e, l) = engine(Settings::default());
+    // A clear note, then low noise the tracker cannot read.
+    let mut x = notes(&[(0.1, 0.6, 55., 0.5)], 0.6);
+    let mut seed = 3u32;
+    let mut lp = 0f32;
+    for _ in 0..seconds(1.5) {
+        seed ^= seed << 13;
+        seed ^= seed >> 17;
+        seed ^= seed << 5;
+        lp += 0.05 * ((seed as f32 / u32::MAX as f32 - 0.5) - lp);
+        x.push(4. * lp);
+    }
+    let solo = render(&mut e, &x, true);
+    let sine = rms(&solo[seconds(0.3) + l..seconds(0.5) + l]);
+    let unsure = rms(&solo[seconds(1.5) + l..seconds(2.0) + l]);
+    assert!(
+        db(unsure) < db(sine) - 40.,
+        "{} vs {}",
+        db(unsure),
+        db(sine)
+    );
+    // The full output carries the original low band again.
+    let (mut e, l) = engine(Settings::default());
+    let y = render(&mut e, &x, false);
+    let a = rms(&x[seconds(1.5)..seconds(2.0)]);
+    let b = rms(&y[seconds(1.5) + l..seconds(2.0) + l]);
+    assert!((db(a) - db(b)).abs() < 1., "{} vs {}", db(a), db(b));
+}
+
+#[test]
+fn enhance_keeps_the_original_and_adds_the_sine() {
+    let x = tones(&[(55., 0.3)], 1.2);
+    for (mode, keeps) in [(Mode::Replace, false), (Mode::Enhance, true)] {
+        let (mut e, l) = engine(Settings {
+            mode,
+            octave: -1,
+            ..Settings::default()
+        });
+        let y = render(&mut e, &x, false);
+        // Whole cycles of 27.5 Hz: 0.4 s.
+        let w = &y[seconds(0.5) + l..seconds(0.9) + l];
+        let original = amplitude(w, 55.);
+        let added = amplitude(w, 27.5);
+        assert!((db(added) + 9.).abs() < 1., "{mode:?}: {}", db(added));
+        if keeps {
+            assert!((db(original) - db(0.3)).abs() < 1., "{}", db(original));
+        } else {
+            assert!(db(original) < db(0.3) - 12., "{}", db(original));
+        }
+    }
+}
+
+#[test]
+fn note_mode_plays_the_set_note_whatever_the_audio() {
+    let (mut e, l) = engine(Settings {
+        source: Source::Note,
+        pitch: common_dsp::tracker::Pitch {
+            note: 29,
+            ..Default::default()
+        },
+        ..Settings::default()
+    });
+    let x = notes(&[(0.1, 1.1, 61.74, 0.5)], 1.3);
+    let y = render(&mut e, &x, true);
+    let f = frequency(&y[seconds(0.3) + l..seconds(1.0) + l]);
+    assert!((f / 43.654 - 1.).abs() < 0.005, "{f}");
+}
@@ -34,7 +34,12 @@ static ALLOCATOR: CheckedAllocator = CheckedAllocator;
 #[test]
 fn processing_notes_settings_and_analysis_do_not_allocate_or_free() {
    let mut engine = Engine::new(48000., 2).unwrap();
-    let mut settings = Settings::default();
+    let mut settings = Settings {
+        ghost: 80.,
+        kick_lock: true,
+        kick_offset: -12.,
+        ..Settings::default()
+    };
    engine.set_settings(settings).unwrap();
    CHECK.with(|v| v.set(true));
    for i in 0..96000 {
@@ -58,7 +63,16 @@ fn processing_notes_settings_and_analysis_do_not_allocate_or_free() {
        } else {
            0.
        };
-        std::hint::black_box(engine.process_sample([x, x], Monitor { solo: i % 3 == 0 }));
+        let kick = if i % 12000 < 400 { 0.8 } else { 0. };
+        std::hint::black_box(engine.process_with_kick(
+            [x, x],
+            kick,
+            Monitor {
+                solo: i % 3 == 0,
+                phone: i % 5 == 0,
+                audition: i > 30000,
+            },
+        ));
        if i % 1600 == 0 {
            std::hint::black_box(engine.take_analyzer());
        }
@@ -72,11 +72,12 @@ checksum = "fc7eb209b1518d6bb87b283c20095f5228ecda460da70b44f0802523dea6da04"

 [[package]]
 name = "anvil"
-version = "0.2.0"
+version = "0.4.0"
 dependencies = [
 "anvil-core",
 "anvil-ui",
 "clap-sys",
+ "common-params",
 "crossbeam-queue",
 "nih_plug",
 "nih_plug_egui",
@@ -340,11 +341,23 @@ dependencies = [
 [[package]]
 name = "common-dsp"
 version = "0.1.0"
+dependencies = [
+ "serde",
+]
+
+[[package]]
+name = "common-params"
+version = "0.1.0"
+dependencies = [
+ "common-dsp",
+ "nih_plug",
+]

 [[package]]
 name = "common-ui"
 version = "0.1.0"
 dependencies = [
+ "common-dsp",
 "egui",
 ]

@@ -1,6 +1,6 @@
 [package]
 name = "anvil"
-version = "0.2.0"
+version = "0.4.0"
 edition = "2021"
 license = "ISC"

@@ -13,6 +13,7 @@ crate-type = ["cdylib", "rlib"]
 nih_plug = { git = "https://github.com/robbert-vdh/nih-plug.git", rev = "de421011f41a6d10fc8c7a6084e4f4dee0143683", default-features = false }
 nih_plug_egui = { git = "https://github.com/robbert-vdh/nih-plug.git", rev = "de421011f41a6d10fc8c7a6084e4f4dee0143683" }
 anvil-core = { path = "../core" }
+common-params = { path = "../../common/params" }
 anvil-ui = { path = "../ui" }
 crossbeam-queue = "0.3"

@@ -13,10 +13,12 @@ use std::sync::{
 struct Shared {
    analyzer: ArrayQueue<AnalyzerFrame>,
    solo: AtomicBool,
+    phone: AtomicBool,
+    audition: AtomicBool,
 }
 struct EditorData {
    ui: anvil_ui::State,
-    gestures: [bool; 9],
+    gestures: [bool; 14],
 }
 pub struct Anvil {
    params: Arc<AnvilParams>,
@@ -32,6 +34,8 @@ impl Default for Anvil {
            shared: Arc::new(Shared {
                analyzer: ArrayQueue::new(2),
                solo: AtomicBool::new(false),
+                phone: AtomicBool::new(false),
+                audition: AtomicBool::new(false),
            }),
            engine: None,
            publish_count: 0,
@@ -49,11 +53,21 @@ impl Plugin for Anvil {
        AudioIOLayout {
            main_input_channels: NonZeroU32::new(2),
            main_output_channels: NonZeroU32::new(2),
+            aux_input_ports: &[new_nonzero_u32(2)],
+            names: PortNames {
+                aux_inputs: &["Kick"],
+                ..PortNames::const_default()
+            },
            ..AudioIOLayout::const_default()
        },
        AudioIOLayout {
            main_input_channels: NonZeroU32::new(1),
            main_output_channels: NonZeroU32::new(1),
+            aux_input_ports: &[new_nonzero_u32(1)],
+            names: PortNames {
+                aux_inputs: &["Kick"],
+                ..PortNames::const_default()
+            },
            ..AudioIOLayout::const_default()
        },
    ];
@@ -71,10 +85,12 @@ impl Plugin for Anvil {
            params.editor.clone(),
            EditorData {
                ui: anvil_ui::State::default(),
-                gestures: [false; 9],
+                gestures: [false; 14],
            },
            |ctx, data| {
                data.ui.solo = false;
+                data.ui.phone = false;
+                data.ui.audition = false;
                anvil_ui::style(ctx);
            },
            move |ctx, setter, data| {
@@ -98,8 +114,11 @@ impl Plugin for Anvil {
                    data.ui.gesture_active,
                    &mut data.gestures,
                );
-                // Solo is a monitor only: never saved and never left on after the editor closes.
+                // Solo and phone listen are monitors only: never saved and never left on
+                // after the editor closes.
                shared.solo.store(data.ui.solo, Ordering::Release);
+                shared.phone.store(data.ui.phone, Ordering::Release);
+                shared.audition.store(data.ui.audition, Ordering::Release);
                if data.ui.analyzer.note.is_some() {
                    ctx.request_repaint();
                }
@@ -125,6 +144,8 @@ impl Plugin for Anvil {
        self.publish_interval = (config.sample_rate / 30.) as usize;
        self.engine = Some(engine);
        self.shared.solo.store(false, Ordering::Release);
+        self.shared.phone.store(false, Ordering::Release);
+        self.shared.audition.store(false, Ordering::Release);
        true
    }
    fn reset(&mut self) {
@@ -136,14 +157,22 @@ impl Plugin for Anvil {
    fn process(
        &mut self,
        buffer: &mut Buffer,
-        _: &mut AuxiliaryBuffers,
+        aux: &mut AuxiliaryBuffers,
        context: &mut impl ProcessContext<Self>,
    ) -> ProcessStatus {
        let Some(engine) = self.engine.as_mut() else {
            return ProcessStatus::Normal;
        };
        let _ = engine.set_settings(self.params.settings());
-        let solo = self.shared.solo.load(Ordering::Acquire) && self.params.editor.is_open();
+        let open = self.params.editor.is_open();
+        let monitor = Monitor {
+            solo: self.shared.solo.load(Ordering::Acquire) && open,
+            phone: self.shared.phone.load(Ordering::Acquire) && open,
+            audition: self.shared.audition.load(Ordering::Acquire) && open,
+        };
+        // A host that does not connect the sidechain still passes a buffer; treat a
+        // missing one as silence.
+        let side = aux.inputs.first().map(|b| b.as_slice_immutable());
        let mut next = context.next_event();
        for (index, mut sample) in buffer.iter_samples().enumerate() {
            while let Some(event) = next {
@@ -170,7 +199,15 @@ impl Plugin for Anvil {
                    0.
                },
            ];
-            let out = engine.process_sample(x, Monitor { solo });
+            let kick = side.map_or(0., |side| {
+                let n = side.len().min(2);
+                side[..n]
+                    .iter()
+                    .map(|c| c.get(index).copied().unwrap_or(0.))
+                    .sum::<f32>()
+                    / n.max(1) as f32
+            });
+            let out = engine.process_with_kick(x, kick, monitor);
            for (c, value) in sample.into_iter().enumerate() {
                *value = out[c];
            }
@@ -1,4 +1,5 @@
-use anvil_core::{Settings, Source};
+use anvil_core::{Mode, Settings, Source, KICK_OFFSET_MAX};
+use common_params::PitchParams;
 use nih_plug::prelude::*;
 use nih_plug_egui::EguiState;
 use std::sync::Arc;
@@ -10,6 +11,49 @@ pub enum SourceParam {
    #[id = "midi"]
    #[name = "MIDI"]
    Midi,
+    #[id = "note"]
+    Note,
+}
+impl From<SourceParam> for Source {
+    fn from(s: SourceParam) -> Self {
+        match s {
+            SourceParam::Audio => Source::Audio,
+            SourceParam::Midi => Source::Midi,
+            SourceParam::Note => Source::Note,
+        }
+    }
+}
+impl From<Source> for SourceParam {
+    fn from(s: Source) -> Self {
+        match s {
+            Source::Audio => SourceParam::Audio,
+            Source::Midi => SourceParam::Midi,
+            Source::Note => SourceParam::Note,
+        }
+    }
+}
+#[derive(Enum, Debug, PartialEq, Eq, Clone, Copy)]
+pub enum ModeParam {
+    #[id = "replace"]
+    Replace,
+    #[id = "enhance"]
+    Enhance,
+}
+impl From<ModeParam> for Mode {
+    fn from(m: ModeParam) -> Self {
+        match m {
+            ModeParam::Replace => Mode::Replace,
+            ModeParam::Enhance => Mode::Enhance,
+        }
+    }
+}
+impl From<Mode> for ModeParam {
+    fn from(m: Mode) -> Self {
+        match m {
+            Mode::Replace => ModeParam::Replace,
+            Mode::Enhance => ModeParam::Enhance,
+        }
+    }
 }
 fn linear(name: &str, v: f32, min: f32, max: f32, unit: &'static str) -> FloatParam {
    FloatParam::new(name, v, FloatRange::Linear { min, max }).with_unit(unit)
@@ -20,6 +64,10 @@ pub struct AnvilParams {
    pub editor: Arc<EguiState>,
    #[id = "source"]
    pub source: EnumParam<SourceParam>,
+    #[nested(group = "Pitch")]
+    pub pitch: PitchParams,
+    #[id = "mode"]
+    pub mode: EnumParam<ModeParam>,
    #[id = "level"]
    pub level: FloatParam,
    #[id = "split"]
@@ -28,6 +76,10 @@ pub struct AnvilParams {
    pub dynamics: FloatParam,
    #[id = "drive"]
    pub drive: FloatParam,
+    #[id = "ghost"]
+    pub ghost: FloatParam,
+    #[id = "ghost_from"]
+    pub ghost_from: FloatParam,
    #[id = "octave"]
    pub octave: IntParam,
    #[id = "glide"]
@@ -46,6 +98,14 @@ pub struct AnvilParams {
    pub snap: BoolParam,
    #[id = "bypass"]
    pub bypass: BoolParam,
+    #[id = "kick_lock"]
+    pub kick_lock: BoolParam,
+    #[id = "kick_duck"]
+    pub kick_duck: FloatParam,
+    #[id = "kick_release"]
+    pub kick_release: FloatParam,
+    #[id = "kick_offset"]
+    pub kick_offset: FloatParam,
 }
 impl Default for AnvilParams {
    fn default() -> Self {
@@ -53,6 +113,8 @@ impl Default for AnvilParams {
        Self {
            editor: EguiState::from_size(anvil_ui::WIDTH, anvil_ui::HEIGHT),
            source: EnumParam::new("Pitch source", SourceParam::Audio),
+            pitch: PitchParams::default(),
+            mode: EnumParam::new("Mode", ModeParam::Replace),
            level: linear("Sub level", d.level, -30., 0., " dBFS"),
            split: FloatParam::new(
                "Split",
@@ -66,6 +128,17 @@ impl Default for AnvilParams {
            .with_unit(" Hz"),
            dynamics: linear("Dynamics", d.dynamics, 0., 100., " %"),
            drive: linear("Drive", d.drive, 0., 100., " %"),
+            ghost: linear("Ghost", d.ghost, 0., 100., " %"),
+            ghost_from: FloatParam::new(
+                "Ghost from",
+                d.ghost_from,
+                FloatRange::Skewed {
+                    min: 150.,
+                    max: 600.,
+                    factor: FloatRange::skew_factor(-1.),
+                },
+            )
+            .with_unit(" Hz"),
            octave: IntParam::new("Octave", d.octave, IntRange::Linear { min: -2, max: 1 }),
            glide: linear("Glide", d.glide, 0., 200., " ms"),
            phase: linear("Phase", d.phase, 0., 360., "°"),
@@ -75,20 +148,31 @@ impl Default for AnvilParams {
            retrigger: BoolParam::new("Retrigger", d.retrigger),
            snap: BoolParam::new("Snap to semitone", d.snap),
            bypass: BoolParam::new("Bypass", false).make_bypass(),
+            kick_lock: BoolParam::new("Kick lock", d.kick_lock),
+            kick_duck: linear("Kick duck", d.kick_duck, 0., 24., " dB"),
+            kick_release: linear("Kick release", d.kick_release, 10., 300., " ms"),
+            kick_offset: linear(
+                "Kick offset",
+                d.kick_offset,
+                -KICK_OFFSET_MAX,
+                KICK_OFFSET_MAX,
+                " ms",
+            ),
        }
    }
 }
 impl AnvilParams {
    pub fn settings(&self) -> Settings {
        Settings {
-            source: match self.source.value() {
-                SourceParam::Audio => Source::Audio,
-                SourceParam::Midi => Source::Midi,
-            },
+            source: self.source.value().into(),
+            pitch: self.pitch.pitch(),
+            mode: self.mode.value().into(),
            level: self.level.value(),
            split: self.split.value(),
            dynamics: self.dynamics.value(),
            drive: self.drive.value(),
+            ghost: self.ghost.value(),
+            ghost_from: self.ghost_from.value(),
            octave: self.octave.value(),
            glide: self.glide.value(),
            phase: self.phase.value(),
@@ -98,6 +182,10 @@ impl AnvilParams {
            retrigger: self.retrigger.value(),
            snap: self.snap.value(),
            bypass: self.bypass.value(),
+            kick_lock: self.kick_lock.value(),
+            kick_duck: self.kick_duck.value(),
+            kick_release: self.kick_release.value(),
+            kick_offset: self.kick_offset.value(),
        }
    }
    /// Pushes every changed editor value to the host. Continuous controls hold one
@@ -108,9 +196,9 @@ impl AnvilParams {
        old: &Settings,
        new: &Settings,
        dragging: bool,
-        open: &mut [bool; 9],
+        open: &mut [bool; 14],
    ) {
-        let floats: [(&FloatParam, f32, f32); 8] = [
+        let floats: [(&FloatParam, f32, f32); 13] = [
            (&self.level, old.level, new.level),
            (&self.split, old.split, new.split),
            (&self.dynamics, old.dynamics, new.dynamics),
@@ -119,6 +207,11 @@ impl AnvilParams {
            (&self.phase, old.phase, new.phase),
            (&self.gate, old.gate, new.gate),
            (&self.keep, old.keep, new.keep),
+            (&self.ghost, old.ghost, new.ghost),
+            (&self.ghost_from, old.ghost_from, new.ghost_from),
+            (&self.kick_duck, old.kick_duck, new.kick_duck),
+            (&self.kick_release, old.kick_release, new.kick_release),
+            (&self.kick_offset, old.kick_offset, new.kick_offset),
        ];
        let mut continuous = |i: usize, changed: bool, set: &dyn Fn()| {
            if changed {
@@ -136,7 +229,7 @@ impl AnvilParams {
        for (i, (p, a, b)) in floats.into_iter().enumerate() {
            continuous(i, a != b, &|| setter.set_parameter(p, b));
        }
-        continuous(8, old.output != new.output, &|| {
+        continuous(13, old.output != new.output, &|| {
            setter.set_parameter(&self.output, new.output)
        });
        let once = |changed: bool, f: &dyn Fn()| {
@@ -153,6 +246,7 @@ impl AnvilParams {
            (&self.retrigger, old.retrigger, new.retrigger),
            (&self.snap, old.snap, new.snap),
            (&self.bypass, old.bypass, new.bypass),
+            (&self.kick_lock, old.kick_lock, new.kick_lock),
        ] {
            once(a != b, &|| {
                setter.begin_set_parameter(p);
@@ -161,14 +255,16 @@ impl AnvilParams {
            });
        }
        once(new.source != old.source, &|| {
-            let v = match new.source {
-                Source::Audio => SourceParam::Audio,
-                Source::Midi => SourceParam::Midi,
-            };
            setter.begin_set_parameter(&self.source);
-            setter.set_parameter(&self.source, v);
+            setter.set_parameter(&self.source, new.source.into());
            setter.end_set_parameter(&self.source);
        });
+        once(new.mode != old.mode, &|| {
+            setter.begin_set_parameter(&self.mode);
+            setter.set_parameter(&self.mode, new.mode.into());
+            setter.end_set_parameter(&self.mode);
+        });
+        self.pitch.apply(setter, &old.pitch, &new.pitch);
    }
    fn continuous(&self, i: usize) -> &FloatParam {
        [
@@ -180,6 +276,11 @@ impl AnvilParams {
            &self.phase,
            &self.gate,
            &self.keep,
+            &self.ghost,
+            &self.ghost_from,
+            &self.kick_duck,
+            &self.kick_release,
+            &self.kick_offset,
            &self.output,
        ][i]
    }
@@ -83,8 +83,9 @@ fn effect_ports_state_latency_and_audio_lifecycle() {
        let ports = p.get_extension.unwrap()(plugin, CLAP_EXT_AUDIO_PORTS.as_ptr())
            as *const clap_plugin_audio_ports;
        assert!(!ports.is_null());
+        // Main input plus the kick sidechain; one output.
+        assert_eq!((*ports).count.unwrap()(plugin, true), 2);
        assert_eq!((*ports).count.unwrap()(plugin, false), 1);
-        assert_eq!((*ports).count.unwrap()(plugin, true), 1);
        let latency = p.get_extension.unwrap()(plugin, CLAP_EXT_LATENCY.as_ptr())
            as *const clap_plugin_latency;
        assert!(!latency.is_null());
@@ -108,6 +109,13 @@ fn effect_ports_state_latency_and_audio_lifecycle() {
            .params
            .insert("level".into(), ParamValue::F32(-14.));
        envelope.params.insert("octave".into(), ParamValue::I32(-1));
+        envelope.params.insert("ghost".into(), ParamValue::F32(40.));
+        envelope
+            .params
+            .insert("kick_lock".into(), ParamValue::Bool(true));
+        envelope
+            .params
+            .insert("kick_offset".into(), ParamValue::F32(-7.));
        envelope
            .params
            .insert("snap".into(), ParamValue::Bool(false));
@@ -154,14 +162,26 @@ fn effect_ports_state_latency_and_audio_lifecycle() {
                let mut left = [0f32; 512];
                let mut right = [0f32; 512];
                let mut in_channels = [input_left.as_mut_ptr(), input_right.as_mut_ptr()];
+                // A connected but silent kick sidechain.
+                let (mut kick_left, mut kick_right) = ([0f32; 512], [0f32; 512]);
+                let mut kick_channels = [kick_left.as_mut_ptr(), kick_right.as_mut_ptr()];
                let mut out_channels = [left.as_mut_ptr(), right.as_mut_ptr()];
-                let incoming = clap_audio_buffer {
-                    data32: in_channels.as_mut_ptr(),
-                    data64: ptr::null_mut(),
-                    channel_count: 2,
-                    latency: 0,
-                    constant_mask: 0,
-                };
+                let incoming = [
+                    clap_audio_buffer {
+                        data32: in_channels.as_mut_ptr(),
+                        data64: ptr::null_mut(),
+                        channel_count: 2,
+                        latency: 0,
+                        constant_mask: 0,
+                    },
+                    clap_audio_buffer {
+                        data32: kick_channels.as_mut_ptr(),
+                        data64: ptr::null_mut(),
+                        channel_count: 2,
+                        latency: 0,
+                        constant_mask: 0,
+                    },
+                ];
                let mut outgoing_audio = clap_audio_buffer {
                    data32: out_channels.as_mut_ptr(),
                    data64: ptr::null_mut(),
@@ -182,9 +202,9 @@ fn effect_ports_state_latency_and_audio_lifecycle() {
                    steady_time: position as i64,
                    frames_count: frames as u32,
                    transport: ptr::null(),
-                    audio_inputs: &incoming,
+                    audio_inputs: incoming.as_ptr(),
                    audio_outputs: &mut outgoing_audio,
-                    audio_inputs_count: 1,
+                    audio_inputs_count: 2,
                    audio_outputs_count: 1,
                    in_events: &input,
                    out_events: &outgoing,
@@ -1,23 +1,35 @@
 //! Anvil editor, shared by the CLAP wrapper and the headless renderer.
-use anvil_core::{AnalyzerFrame, Settings, Source, SCOPE};
+use anvil_core::{
+    AnalyzerFrame, Mode, Settings, Source, AUDITION, AUDITION_HITS, GHOST_COUNT, KICK_OFFSET_MAX,
+    PHONE_LOW, SCOPE,
+};
 use common_ui::*;
 use egui::{self, Color32, FontId, Pos2, RichText, Sense, Stroke, Vec2};

 pub use common_ui::style;
 pub const WIDTH: u32 = 980;
-pub const HEIGHT: u32 = 704;
+pub const HEIGHT: u32 = 872;

 pub struct State {
    pub solo: bool,
+    /// Phone-like listen. A monitor, never saved.
+    pub phone: bool,
+    /// Kick offset audition. A monitor, never saved.
+    pub audition: bool,
    pub analyzer: AnalyzerFrame,
    /// True while a pointer button is held, so knob drags become one host gesture.
    pub gesture_active: bool,
    pub help: String,
+    /// The advanced page shows instead of the main one. Not saved.
+    pub advanced: bool,
 }
 impl Default for State {
    fn default() -> Self {
        Self {
+            advanced: false,
            solo: false,
+            phone: false,
+            audition: false,
            analyzer: AnalyzerFrame::default(),
            gesture_active: false,
            help: DEFAULT_HELP.into(),
@@ -64,7 +76,63 @@ fn toggle(ui: &mut egui::Ui, state: &mut State, on: &mut bool, label: &str, help
    }
    hint(&r, state, help);
 }
-fn scope(ui: &mut egui::Ui, frame: &AnalyzerFrame, height: f32) {
+/// Harmonics 2–10 of the current note: what the patch carries above the split (steel)
+/// and what Ghost adds (accent), from −48 dB to 0 dB against the sub.
+fn harmonics(p: &egui::Painter, rect: egui::Rect, frame: &AnalyzerFrame) {
+    p.rect_filled(rect, 2., Color32::from_rgba_unmultiplied(12, 13, 16, 230));
+    p.rect_stroke(
+        rect,
+        2.,
+        Stroke::new(1.0_f32, EDGE),
+        egui::StrokeKind::Inside,
+    );
+    p.text(
+        rect.left_top() + Vec2::new(8., 6.),
+        egui::Align2::LEFT_TOP,
+        "GHOST",
+        FontId::proportional(10.),
+        ACCENT,
+    );
+    p.text(
+        rect.right_top() + Vec2::new(-8., 6.),
+        egui::Align2::RIGHT_TOP,
+        format!("from {:.0} Hz", frame.ghost_edge),
+        FontId::proportional(10.),
+        MUTED,
+    );
+    let area = egui::Rect::from_min_max(
+        rect.left_top() + Vec2::new(8., 22.),
+        rect.right_bottom() - Vec2::new(8., 16.),
+    );
+    let slot = area.width() / GHOST_COUNT as f32;
+    let height = |db: f32| ((db + 48.) / 48.).clamp(0., 1.) * area.height();
+    for i in 0..GHOST_COUNT {
+        let x = area.left() + slot * i as f32;
+        let bar = |left: f32, db: f32, color: Color32| {
+            let h = height(db);
+            if h > 0.5 {
+                p.rect_filled(
+                    egui::Rect::from_min_max(
+                        Pos2::new(left, area.bottom() - h),
+                        Pos2::new(left + slot * 0.36, area.bottom()),
+                    ),
+                    1.,
+                    color,
+                );
+            }
+        };
+        bar(x + slot * 0.12, frame.patch_harmonics[i], STEEL);
+        bar(x + slot * 0.52, frame.ghost_harmonics[i], ACCENT);
+        p.text(
+            Pos2::new(x + slot * 0.5, area.bottom() + 2.),
+            egui::Align2::CENTER_TOP,
+            format!("{}", i + 2),
+            FontId::proportional(9.),
+            DIM,
+        );
+    }
+}
+fn scope(ui: &mut egui::Ui, frame: &AnalyzerFrame, height: f32, ghost: bool) {
    let (rect, _) = ui.allocate_exact_size(Vec2::new(ui.available_width(), height), Sense::hover());
    let p = ui.painter_at(rect);
    p.rect_filled(rect, 2., SCREEN);
@@ -123,6 +191,11 @@ fn scope(ui: &mut egui::Ui, frame: &AnalyzerFrame, height: f32) {
        FontId::proportional(11.),
        MUTED,
    );
+    if ghost {
+        let size = Vec2::new(200., 92.);
+        let corner = rect.right_bottom() - Vec2::new(8., 8.);
+        harmonics(&p, egui::Rect::from_min_max(corner - size, corner), frame);
+    }
    p.rect_stroke(
        rect,
        2.,
@@ -136,7 +209,8 @@ pub fn show(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
    state.help = DEFAULT_HELP.into();
    state.gesture_active = ui.input(|i| i.pointer.any_down());
    ui.add_space(2.);
-    header(ui, "ANVIL", "SUB ANCHOR", |ui| {
+    let mut advanced = state.advanced;
+    header_paged(ui, "ANVIL", "SUB ANCHOR", Some(&mut advanced), |ui| {
        let r = ui
            .selectable_label(settings.bypass, RichText::new("BYPASS").size(13.))
            .on_hover_text("Crossfade to the delayed dry signal.");
@@ -145,19 +219,24 @@ pub fn show(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
        }
        let r = ui
            .selectable_label(state.solo, RichText::new("SOLO SUB").size(13.))
-            .on_hover_text("Hear only the generated sub.");
+            .on_hover_text("Hear only the generated sub and Ghost harmonics.");
        if r.clicked() {
            state.solo = !state.solo;
        }
-        ui.separator();
-        for (source, label) in [(Source::Midi, "MIDI"), (Source::Audio, "AUDIO")] {
-            let r = ui.selectable_label(settings.source == source, RichText::new(label).size(13.));
-            if r.clicked() {
-                settings.source = source;
-            }
+        let r = ui
+            .selectable_label(state.phone, RichText::new("PHONE").size(13.))
+            .on_hover_text(format!(
+                "Listen as on a phone: mono, nothing below {PHONE_LOW:.0} Hz. Not saved."
+            ));
+        if r.clicked() {
+            state.phone = !state.phone;
        }
-        caption(ui, "PITCH FROM");
+        ui.separator();
+        let mut mode = settings.source.mode();
+        pitch_from(ui, &mut mode, &mut settings.pitch);
+        settings.source = Source::from_mode(mode);
    });
+    state.advanced = advanced;
    ui.add_space(6.);
    let frame = state.analyzer;
    ui.horizontal_top(|ui| {
@@ -169,14 +248,28 @@ pub fn show(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
        ui.add_space(4.);
        panel(ui, |ui| {
            ui.set_width(ui.available_width());
-            scope(ui, &frame, TOP);
+            scope(ui, &frame, TOP, settings.ghost > 0.);
        });
    });
    ui.add_space(6.);
-    panel(ui, |ui| {
-        ui.set_width(ui.available_width());
-        ui.vertical(|ui| controls(ui, settings, state));
-    });
+    if state.advanced {
+        panel(ui, |ui| {
+            ui.set_width(ui.available_width());
+            ui.vertical(|ui| controls(ui, settings, state));
+        });
+        ui.add_space(6.);
+        panel(ui, |ui| {
+            ui.set_width(ui.available_width());
+            kick_panel(ui, settings, state);
+        });
+    } else {
+        let height = ui.available_height() - 64.;
+        panel(ui, |ui| {
+            ui.set_width(ui.available_width());
+            ui.set_min_height(height);
+            ui.vertical(|ui| main_controls(ui, settings, state));
+        });
+    }
    ui.separator();
    ui.label(RichText::new(&state.help).color(MUTED));
 }
@@ -185,6 +278,7 @@ fn note_panel(ui: &mut egui::Ui, settings: &Settings, frame: &AnalyzerFrame) {
    caption(ui, "NOTE");
    let (name, hz) = match frame.note {
        Some(n) if frame.hz > 0. => (common_dsp::note_name(n), format!("{:.1} Hz", frame.hz)),
+        _ if frame.neutral => ("?".into(), "unsure: original sub plays".into()),
        _ => ("—".into(), "no note".into()),
    };
    ui.label(
@@ -201,18 +295,140 @@ fn note_panel(ui: &mut egui::Ui, settings: &Settings, frame: &AnalyzerFrame) {
        RichText::new(format!(
            "{:.0} ms lookahead · {}",
            frame.latency as f32 / frame.sample_rate * 1000.,
-            match settings.source {
-                Source::Audio => "detecting pitch",
-                Source::Midi => "following MIDI notes",
-            }
+            pitch_status(settings.source.mode(), &settings.pitch)
        ))
        .size(12.)
        .color(MUTED),
    );
 }
+/// The main page: what happens to the original sub, where the sub ends and how loud the
+/// new one plays.
+fn main_controls(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
+    let defaults = Settings::default();
+    ui.add_space(24.);
+    ui.columns(3, |c| {
+        c[0].vertical_centered(|ui| {
+            caption(ui, "MODE");
+            ui.add_space(6.);
+            ui.spacing_mut().item_spacing.x = 8.;
+            let r = choice(
+                ui,
+                &mut settings.mode,
+                &[
+                    (
+                        Mode::Replace,
+                        "REPLACE",
+                        "Swap the sub below Split for a clean sine: one level and phase on every note.",
+                    ),
+                    (
+                        Mode::Enhance,
+                        "ENHANCE",
+                        "Keep the original sub and add the clean sine under it for weight.",
+                    ),
+                ],
+            );
+            if let Some(r) = r {
+                hint(&r, state, "Replace swaps the sub; Enhance keeps it and adds weight.");
+            }
+            ui.add_space(14.);
+            let text = match settings.mode {
+                Mode::Replace => {
+                    "The band below Split is replaced by a clean sine on the played note. \
+                     Every note gets the same level and starts at the same phase."
+                }
+                Mode::Enhance => {
+                    "Your sub stays as it is. A clean sine on the played note is added \
+                     under it. Try Octave −1 for a sub-octave."
+                }
+            };
+            ui.label(RichText::new(text).size(13.).color(MUTED));
+            ui.add_space(10.);
+            ui.label(
+                RichText::new(
+                    "When the note is unclear, Anvil plays your original sub instead of guessing.",
+                )
+                .size(12.)
+                .color(DIM),
+            );
+        });
+        knob(
+            &mut c[1],
+            state,
+            "Split",
+            &mut settings.split,
+            40. ..=200.,
+            defaults.split,
+            " Hz",
+            120.,
+            "Set it just above the sub. Below it the sub is replaced (or enhanced).",
+        );
+        knob(
+            &mut c[2],
+            state,
+            "Sub level",
+            &mut settings.level,
+            -30. ..=0.,
+            defaults.level,
+            " dBFS",
+            120.,
+            "Peak level of the new sub. Every note gets exactly this level.",
+        );
+    });
+    ui.add_space(28.);
+    ui.separator();
+    ui.add_space(12.);
+    ui.columns(4, |c| {
+        let mut octave = settings.octave as f32;
+        knob(
+            &mut c[0],
+            state,
+            "Octave",
+            &mut octave,
+            -2. ..=1.,
+            0.,
+            "",
+            64.,
+            "Move the new sub up or down an octave against the played note.",
+        );
+        settings.octave = octave.round() as i32;
+        knob(
+            &mut c[1],
+            state,
+            "Ghost",
+            &mut settings.ghost,
+            0. ..=100.,
+            defaults.ghost,
+            " %",
+            64.,
+            "Lets phones and laptops hear the sub note: adds its harmonics the patch lacks.",
+        );
+        knob(
+            &mut c[2],
+            state,
+            "Keep",
+            &mut settings.keep,
+            0. ..=100.,
+            defaults.keep,
+            " %",
+            64.,
+            "Blend some of the original sub back under the new one (Replace mode).",
+        );
+        knob(
+            &mut c[3],
+            state,
+            "Output",
+            &mut settings.output,
+            -12. ..=12.,
+            defaults.output,
+            " dB",
+            64.,
+            "Output trim.",
+        );
+    });
+}
 fn controls(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
    let defaults = Settings::default();
-    ui.columns(4, |c| {
+    ui.columns(6, |c| {
        knob(
            &mut c[0],
            state,
@@ -255,7 +471,30 @@ fn controls(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
            defaults.drive,
            " %",
            88.,
-            "Adds upper harmonics so the sub reads on small speakers.",
+            "Saturates the sine: odd harmonics, thicker sub. Changes the sub itself.",
+        );
+        knob(
+            &mut c[4],
+            state,
+            "Ghost",
+            &mut settings.ghost,
+            0. ..=100.,
+            defaults.ghost,
+            " %",
+            88.,
+            "Adds the sub's harmonics 2–10 above Ghost from, so phones hear the note. \
+             Only harmonics the patch lacks are added. The sub itself stays the same.",
+        );
+        knob(
+            &mut c[5],
+            state,
+            "Ghost from",
+            &mut settings.ghost_from,
+            150. ..=600.,
+            defaults.ghost_from,
+            " Hz",
+            88.,
+            "Lowest frequency Ghost adds. Phones cut off around 300–500 Hz. Never below Split.",
        );
    });
    ui.add_space(6.);
@@ -346,5 +585,170 @@ fn controls(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
            "SNAP TO SEMITONE",
            "Round the detected pitch. Turn off for slides and pitch bends.",
        );
+        ui.separator();
+        caption(ui, "MODE");
+        for (mode, label, help) in [
+            (
+                Mode::Replace,
+                "REPLACE",
+                "Swap the sub below Split for the clean sine.",
+            ),
+            (
+                Mode::Enhance,
+                "ENHANCE",
+                "Keep the original sub and add the sine under it.",
+            ),
+        ] {
+            let r = ui.selectable_label(settings.mode == mode, RichText::new(label).size(13.));
+            if r.clicked() {
+                settings.mode = mode;
+            }
+            hint(&r, state, help);
+        }
    });
 }
+fn kick_panel(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
+    let defaults = Settings::default();
+    let frame = state.analyzer;
+    ui.horizontal_top(|ui| {
+        ui.vertical(|ui| {
+            ui.set_width(150.);
+            caption(ui, "KICK LOCK");
+            toggle(
+                ui,
+                state,
+                &mut settings.kick_lock,
+                "KICK LOCK",
+                "Route the kick into Anvil's sidechain. On each kick the sub dips and \
+                 restarts at Phase, so kick and sub hit together.",
+            );
+            ui.add_space(6.);
+            let status = if !settings.kick_lock {
+                "off".to_string()
+            } else if frame.kick_hits == 0 {
+                "no kick in the sidechain".to_string()
+            } else if frame.kick_sum_db.is_finite() {
+                format!("{} kicks · sum {:+.1} dB", frame.kick_hits, frame.kick_sum_db)
+            } else {
+                format!("{} kicks", frame.kick_hits)
+            };
+            ui.label(RichText::new(status).size(12.).color(MUTED));
+        });
+        ui.columns(4, |c| {
+            knob(
+                &mut c[0],
+                state,
+                "Duck",
+                &mut settings.kick_duck,
+                0. ..=24.,
+                defaults.kick_duck,
+                " dB",
+                54.,
+                "How far the sub dips on each kick.",
+            );
+            knob(
+                &mut c[1],
+                state,
+                "Release",
+                &mut settings.kick_release,
+                10. ..=300.,
+                defaults.kick_release,
+                " ms",
+                54.,
+                "Time for the sub to come back after a kick.",
+            );
+            knob(
+                &mut c[2],
+                state,
+                "Offset",
+                &mut settings.kick_offset,
+                -KICK_OFFSET_MAX..=KICK_OFFSET_MAX,
+                defaults.kick_offset,
+                " ms",
+                54.,
+                "When the sub restarts against the kick. Negative: before it. Use Audition to find it by ear.",
+            );
+            c[3].vertical(|ui| audition(ui, settings, state));
+        });
+    });
+}
+/// The audition: each offset plays for a few kicks; bars show how kick and sub summed.
+fn audition(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
+    let frame = state.analyzer;
+    ui.horizontal(|ui| {
+        let r = ui.selectable_label(state.audition, RichText::new("AUDITION").size(12.));
+        if r.clicked() {
+            state.audition = !state.audition;
+        }
+        hint(
+            &r,
+            state,
+            &format!(
+                "Steps the offset from −30 to +30 ms, {AUDITION_HITS} kicks each. Press KEEP \
+                 when kick and sub sound like one hit. Not saved."
+            ),
+        );
+        let r = ui.add_enabled(
+            state.audition && frame.kick_hits > 0,
+            egui::Button::new(RichText::new("KEEP").size(12.)),
+        );
+        if r.clicked() {
+            settings.kick_offset = frame.kick_offset;
+            state.audition = false;
+        }
+        hint(
+            &r,
+            state,
+            "Set Offset to the one playing now and stop the audition.",
+        );
+    });
+    let (rect, _) = ui.allocate_exact_size(Vec2::new(ui.available_width(), 58.), Sense::hover());
+    let p = ui.painter_at(rect);
+    p.rect_filled(rect, 2., SCREEN);
+    let slot = rect.width() / AUDITION.len() as f32;
+    // −9 dB to +3 dB: +3 is a full sum of equal levels.
+    let height = |db: f32| ((db + 9.) / 12.).clamp(0.02, 1.) * (rect.height() - 14.);
+    for (i, &offset) in AUDITION.iter().enumerate() {
+        let x = rect.left() + slot * i as f32;
+        let db = frame.audition_sums[i];
+        let playing = state.audition && (offset - frame.kick_offset).abs() < 0.01;
+        if db.is_finite() {
+            let h = height(db);
+            p.rect_filled(
+                egui::Rect::from_min_max(
+                    Pos2::new(x + slot * 0.2, rect.bottom() - 12. - h),
+                    Pos2::new(x + slot * 0.8, rect.bottom() - 12.),
+                ),
+                1.,
+                if playing { ACCENT } else { STEEL },
+            );
+        }
+        if (offset - settings.kick_offset).abs() < 0.01 {
+            // The kept offset.
+            let (cx, base) = (x + slot * 0.5, rect.bottom() - 2.);
+            p.add(egui::Shape::convex_polygon(
+                vec![
+                    Pos2::new(cx, base - 7.),
+                    Pos2::new(cx + 4., base),
+                    Pos2::new(cx - 4., base),
+                ],
+                ACCENT,
+                Stroke::NONE,
+            ));
+        } else if i % 2 == 0 {
+            p.text(
+                Pos2::new(x + slot * 0.5, rect.bottom() - 1.),
+                egui::Align2::CENTER_BOTTOM,
+                format!("{offset:+.0}"),
+                FontId::proportional(8.),
+                DIM,
+            );
+        }
+    }
+    let line = if state.audition {
+        format!("playing {:+.0} ms", frame.kick_offset)
+    } else {
+        "sum per offset, low band".into()
+    };
+    ui.label(RichText::new(line).size(11.).color(MUTED));
+}
@@ -0,0 +1,12 @@
+[package]
+name = "ballast-core"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+common-dsp = { path = "../../common/dsp" }
+serde = { workspace = true }
+
+[dev-dependencies]
+serde_json = { workspace = true }
@@ -0,0 +1,482 @@
+//! Levels each part of a bassline, a note or a step of the beat grid, to one loudness with a
+//! single gain per part. No compression: the gain does not move inside a part, so a patch
+//! keeps its own envelope and punch.
+//!
+//! A part's loudness is the K-weighted (ITU-R BS.1770) mean square of its first 100 ms, or
+//! of all of it when it is shorter, counted in 10 ms blocks; blocks 20 dB under the loudest
+//! one are left out, so a gap at the start does not pull the reading down. Each part is
+//! weighted from rest, as if it played alone. The audio path is delayed by the note tracker's lookahead
+//! plus that window plus a 5 ms ramp, so every part's gain is known before its attack leaves
+//! the plugin, and the ramp to it ends exactly on the attack.
+mod settings;
+use common_dsp::loudness::{lufs, KWeighting};
+use common_dsp::svf::{Svf, SvfCoef};
+use common_dsp::tracker::{NoteEvent, PitchMode, PitchSource, Tracker, TrackerConfig};
+use common_dsp::{coefficient, db_to_gain, gain_to_db};
+pub use settings::{
+    Grid, Segment, Settings, Source, FROM_MAX, FROM_MIN, RANGE_MAX, TARGET_MAX, TARGET_MIN,
+};
+
+/// Each part is measured over this much of its start.
+pub const WINDOW_MS: f32 = 100.;
+/// The gain glides to a new part's value over this long, ending on its first sample.
+pub const RAMP_MS: f32 = 5.;
+/// A boundary closer than this to the last one is ignored: the parts are merged.
+const MIN_PART_MS: f32 = 10.;
+/// The window is measured in blocks of this length.
+const BLOCK_MS: f32 = 10.;
+const BLOCKS: usize = (WINDOW_MS / BLOCK_MS) as usize;
+/// Blocks this far under the part's loudest block do not count: a note start found by a
+/// pitch change can come early, inside the gap before the note.
+const RELATIVE_GATE_DB: f64 = 20.;
+/// Parts shown in the editor.
+pub const HISTORY: usize = 32;
+/// Parts used for the spread readout.
+const SPREAD: usize = 16;
+const PENDING: usize = 32;
+const Q: f32 = std::f32::consts::FRAC_1_SQRT_2;
+/// Tempo the grid runs at before the host reports one.
+const FALLBACK_BPM: f64 = 120.;
+
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+pub struct Part {
+    /// Loudness of the part's measured start, in LUFS.
+    pub loudness: f32,
+    /// Gain given to the part, in dB.
+    pub gain: f32,
+    /// Under the gate: the part kept the previous gain.
+    pub gated: bool,
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct AnalyzerFrame {
+    /// Latest parts, oldest first; the first `count` entries are valid.
+    pub history: [Part; HISTORY],
+    pub count: usize,
+    /// Gain applied at the output right now, in dB.
+    pub gain: f32,
+    /// Standard deviation of the loudness of the last 16 parts over the gate, before and after
+    /// Ballast. NaN with fewer than two.
+    pub spread_in: f32,
+    pub spread_out: f32,
+    /// Waiting for the next part to take as the target.
+    pub learning: bool,
+    /// The loudness last taken by Learn, and a number that changes each time one is taken.
+    pub learned: f32,
+    pub learn_id: u32,
+    pub tempo: f64,
+    pub synced: bool,
+    pub latency: u32,
+    pub sample_rate: f32,
+}
+impl Default for AnalyzerFrame {
+    fn default() -> Self {
+        Self {
+            history: [Part::default(); HISTORY],
+            count: 0,
+            gain: 0.,
+            spread_in: f32::NAN,
+            spread_out: f32::NAN,
+            learning: false,
+            learned: f32::NAN,
+            learn_id: 0,
+            tempo: FALLBACK_BPM,
+            synced: false,
+            latency: 0,
+            sample_rate: 48000.,
+        }
+    }
+}
+
+/// Gain in dB that brings `loudness` to the target, at `amount` (0–1), within ±`range`.
+pub fn part_gain(loudness: f32, target: f32, amount: f32, range: f32) -> f32 {
+    ((target - loudness) * amount).clamp(-range, range)
+}
+
+#[derive(Clone, Copy, Default)]
+struct Pending {
+    start: u64,
+    gain: f32,
+}
+
+pub struct Engine {
+    rate: f32,
+    channels: usize,
+    settings: Settings,
+    tracker: Tracker,
+    lookahead: usize,
+    window: usize,
+    ramp: usize,
+    min_part: usize,
+    delay: Vec<[f32; 2]>,
+    delay_at: usize,
+    weighting: [KWeighting; 2],
+    from: [[Svf; 2]; 2],
+    from_coef: SvfCoef,
+    /// Samples of the aligned stream: the input delayed by the tracker's lookahead.
+    clock: u64,
+    open: bool,
+    part_start: u64,
+    block: usize,
+    blocks: [(f64, usize); BLOCKS],
+    measured: usize,
+    last_gain: f32,
+    queue: [Pending; PENDING],
+    queue_head: usize,
+    queue_len: usize,
+    gain: f32,
+    ramp_from: f32,
+    ramp_to: f32,
+    ramp_left: usize,
+    history: [Part; HISTORY],
+    history_at: usize,
+    history_len: usize,
+    learn: bool,
+    learned: f32,
+    learn_id: u32,
+    tempo: f64,
+    /// Beat position of the aligned stream.
+    beats: f64,
+    synced: bool,
+    cell: i64,
+    output: f32,
+    bypass: f32,
+    smooth: f32,
+    fresh: bool,
+}
+
+impl Engine {
+    pub fn new(rate: f32, channels: usize) -> Result<Self, &'static str> {
+        if !(8000.0..=384000.).contains(&rate) {
+            return Err("unsupported sample rate");
+        }
+        if !(1..=2).contains(&channels) {
+            return Err("unsupported channel count");
+        }
+        let tracker = Tracker::new(rate, TrackerConfig::BASS);
+        let lookahead = tracker.latency();
+        let samples = |ms: f32| ((rate * ms * 0.001).round() as usize).max(1);
+        let (window, ramp) = (samples(WINDOW_MS), samples(RAMP_MS));
+        let mut e = Self {
+            rate,
+            channels,
+            settings: Settings::default(),
+            tracker,
+            lookahead,
+            window,
+            ramp,
+            min_part: samples(MIN_PART_MS),
+            delay: vec![[0.; 2]; lookahead + window + ramp + 1],
+            delay_at: 0,
+            weighting: [KWeighting::new(rate); 2],
+            from: [[Svf::default(); 2]; 2],
+            from_coef: SvfCoef::IDENTITY,
+            clock: 0,
+            open: false,
+            part_start: 0,
+            block: samples(BLOCK_MS),
+            blocks: [(0., 0); BLOCKS],
+            measured: 0,
+            last_gain: 0.,
+            queue: [Pending::default(); PENDING],
+            queue_head: 0,
+            queue_len: 0,
+            gain: 1.,
+            ramp_from: 1.,
+            ramp_to: 1.,
+            ramp_left: 0,
+            history: [Part::default(); HISTORY],
+            history_at: 0,
+            history_len: 0,
+            learn: false,
+            learned: f32::NAN,
+            learn_id: 0,
+            tempo: FALLBACK_BPM,
+            beats: 0.,
+            synced: false,
+            cell: 0,
+            output: 1.,
+            bypass: 0.,
+            smooth: coefficient(rate, 10.),
+            fresh: true,
+        };
+        e.set_settings(Settings::default())?;
+        e.fresh = true;
+        Ok(e)
+    }
+    /// Lookahead of the tracker, the measuring window and the ramp.
+    pub fn latency_samples(&self) -> u32 {
+        (self.lookahead + self.window + self.ramp) as u32
+    }
+    pub fn channels(&self) -> usize {
+        self.channels
+    }
+    pub fn settings(&self) -> Settings {
+        self.settings
+    }
+    pub fn set_settings(&mut self, s: Settings) -> Result<(), &'static str> {
+        s.validate()?;
+        self.tracker.set(PitchSource {
+            mode: if s.source == Source::Midi {
+                PitchMode::Midi
+            } else {
+                PitchMode::Audio
+            },
+            gate_db: s.gate,
+            ..PitchSource::default()
+        });
+        if s.from != self.settings.from || self.fresh {
+            self.from_coef = if s.from > FROM_MIN {
+                SvfCoef::highpass(self.rate, s.from, Q)
+            } else {
+                SvfCoef::IDENTITY
+            };
+        }
+        self.settings = s;
+        if std::mem::take(&mut self.fresh) {
+            self.output = db_to_gain(s.output);
+            self.bypass = f32::from(s.bypass);
+        }
+        Ok(())
+    }
+    /// Host tempo in BPM and, while playing, the beat position at the block's first sample.
+    pub fn set_transport(&mut self, tempo: Option<f64>, position: Option<f64>) {
+        if let Some(t) = tempo.filter(|t| t.is_finite() && *t > 0.) {
+            self.tempo = t;
+        }
+        match position.filter(|p| p.is_finite()) {
+            Some(p) => {
+                // The parts are cut on the aligned stream, `lookahead` samples behind the input.
+                self.beats = p - self.lookahead as f64 / self.rate as f64 * self.tempo / 60.;
+                self.synced = true;
+            }
+            None => self.synced = false,
+        }
+    }
+    pub fn note_on(&mut self, note: u8) {
+        self.tracker.note_on(note);
+    }
+    pub fn note_off(&mut self, note: u8) {
+        self.tracker.note_off(note);
+    }
+    /// Takes the loudness of the next part over the gate as the new target.
+    pub fn learn(&mut self) {
+        self.learn = true;
+    }
+    pub fn reset(&mut self) {
+        self.tracker.reset();
+        self.delay.fill([0.; 2]);
+        self.delay_at = 0;
+        for k in &mut self.weighting {
+            k.reset();
+        }
+        self.from = [[Svf::default(); 2]; 2];
+        self.clock = 0;
+        self.open = false;
+        self.blocks = [(0., 0); BLOCKS];
+        self.measured = 0;
+        self.last_gain = 0.;
+        self.queue_len = 0;
+        self.gain = 1.;
+        self.ramp_left = 0;
+        self.history_len = 0;
+        self.learn = false;
+        self.fresh = true;
+        let s = self.settings;
+        let _ = self.set_settings(s);
+    }
+
+    /// Mean square of the measured blocks, without those far under the loudest.
+    fn gated_mean(&self) -> f64 {
+        let used = self.measured.div_ceil(self.block).min(BLOCKS);
+        let blocks = &self.blocks[..used];
+        let loudest = blocks
+            .iter()
+            .map(|(s, n)| s / (*n).max(1) as f64)
+            .fold(0., f64::max);
+        let floor = loudest * 10f64.powf(-RELATIVE_GATE_DB / 10.);
+        let (sum, n) = blocks
+            .iter()
+            .filter(|(s, n)| s / (*n).max(1) as f64 >= floor)
+            .fold((0., 0), |(a, b), (s, n)| (a + s, b + n));
+        sum / n.max(1) as f64
+    }
+    fn close(&mut self) {
+        self.open = false;
+        let s = self.settings;
+        let loudness = lufs(self.gated_mean());
+        let gated = loudness < s.gate;
+        let gain = if gated {
+            self.last_gain
+        } else {
+            part_gain(loudness, s.target, s.amount * 0.01, s.range)
+        };
+        if !gated {
+            self.last_gain = gain;
+            if std::mem::take(&mut self.learn) {
+                self.learned = loudness;
+                self.learn_id = self.learn_id.wrapping_add(1);
+            }
+        }
+        if self.queue_len < PENDING {
+            let at = (self.queue_head + self.queue_len) % PENDING;
+            self.queue[at] = Pending {
+                start: self.part_start,
+                gain,
+            };
+            self.queue_len += 1;
+        }
+        self.history[self.history_at] = Part {
+            loudness,
+            gain,
+            gated,
+        };
+        self.history_at = (self.history_at + 1) % HISTORY;
+        self.history_len = (self.history_len + 1).min(HISTORY);
+    }
+
+    // Channels index the delayed frame, the filters and the output at once.
+    #[allow(clippy::needless_range_loop)]
+    pub fn process_sample(&mut self, x: [f32; 2]) -> [f32; 2] {
+        let mono = if self.channels == 2 {
+            0.5 * (x[0] + x[1])
+        } else {
+            x[0]
+        };
+        let mut started = false;
+        self.tracker.process(mono, |e| {
+            if matches!(e, NoteEvent::Start { .. }) {
+                started = true;
+            }
+        });
+        let len = self.delay.len();
+        self.delay[self.delay_at] = x;
+        let aligned = self.delay[(self.delay_at + len - self.lookahead) % len];
+        self.delay_at = (self.delay_at + 1) % len;
+        let delayed = self.delay[self.delay_at];
+
+        // Grid lines are counted on the aligned stream even in Notes mode, so switching modes
+        // does not cut a part.
+        let cell = (self.beats / self.settings.grid.quarters()).floor() as i64;
+        self.beats += self.tempo / 60. / self.rate as f64;
+        let crossed = cell != self.cell;
+        self.cell = cell;
+        let boundary = match self.settings.segment {
+            Segment::Notes => started,
+            Segment::Grid => crossed,
+        };
+
+        if boundary && !(self.open && self.measured < self.min_part) {
+            if self.open {
+                self.close();
+            }
+            self.open = true;
+            self.part_start = self.clock;
+            self.blocks = [(0., 0); BLOCKS];
+            self.measured = 0;
+            // Each part is weighted from rest, as if it played alone: the filters' memory of
+            // the last part would otherwise ring into this one.
+            for k in &mut self.weighting {
+                k.reset();
+            }
+            self.from = [[Svf::default(); 2]; 2];
+        }
+        let mut power = 0f64;
+        for c in 0..self.channels {
+            let f = &mut self.from[c];
+            let v = f[0].process(&self.from_coef, aligned[c]);
+            let v = f[1].process(&self.from_coef, v);
+            let w = self.weighting[c].process(v) as f64;
+            power += w * w;
+        }
+        if self.open {
+            let b = &mut self.blocks[(self.measured / self.block).min(BLOCKS - 1)];
+            b.0 += power;
+            b.1 += 1;
+            self.measured += 1;
+            if self.measured >= self.window {
+                self.close();
+            }
+        }
+        // A part's ramp starts `ramp` samples before its first sample reaches the output.
+        if self.queue_len > 0 {
+            let next = self.queue[self.queue_head];
+            if self.clock >= next.start + self.window as u64 {
+                self.queue_head = (self.queue_head + 1) % PENDING;
+                self.queue_len -= 1;
+                self.ramp_from = self.gain;
+                self.ramp_to = db_to_gain(next.gain);
+                self.ramp_left = self.ramp;
+            }
+        }
+        if self.ramp_left > 0 {
+            self.ramp_left -= 1;
+            let t = 1. - self.ramp_left as f32 / self.ramp as f32;
+            let t = t * t * (3. - 2. * t);
+            self.gain = self.ramp_from + (self.ramp_to - self.ramp_from) * t;
+        }
+        self.clock += 1;
+
+        let s = self.settings;
+        self.output += (db_to_gain(s.output) - self.output) * self.smooth;
+        self.bypass += (f32::from(s.bypass) - self.bypass) * self.smooth;
+        if (f32::from(s.bypass) - self.bypass).abs() < 1e-6 {
+            self.bypass = f32::from(s.bypass);
+        }
+        let mut out = [0.; 2];
+        for c in 0..self.channels {
+            let wet = delayed[c] * self.gain * self.output;
+            out[c] = if self.bypass >= 1. {
+                delayed[c]
+            } else {
+                wet + (delayed[c] - wet) * self.bypass
+            };
+        }
+        out
+    }
+
+    fn spread(&self, after: bool) -> f32 {
+        let (mut n, mut sum, mut sq) = (0usize, 0f64, 0f64);
+        for i in 0..self.history_len {
+            if n == SPREAD {
+                break;
+            }
+            let p = self.history[(self.history_at + HISTORY - 1 - i) % HISTORY];
+            if p.gated {
+                continue;
+            }
+            let v = (p.loudness + if after { p.gain } else { 0. }) as f64;
+            n += 1;
+            sum += v;
+            sq += v * v;
+        }
+        if n < 2 {
+            return f32::NAN;
+        }
+        let mean = sum / n as f64;
+        ((sq / n as f64 - mean * mean).max(0.)).sqrt() as f32
+    }
+
+    /// Readings for the editor. Never allocates.
+    pub fn take_analyzer(&self) -> AnalyzerFrame {
+        let mut f = AnalyzerFrame {
+            count: self.history_len,
+            gain: gain_to_db(self.gain),
+            spread_in: self.spread(false),
+            spread_out: self.spread(true),
+            learning: self.learn,
+            learned: self.learned,
+            learn_id: self.learn_id,
+            tempo: self.tempo,
+            synced: self.synced,
+            latency: self.latency_samples(),
+            sample_rate: self.rate,
+            ..AnalyzerFrame::default()
+        };
+        let first = (self.history_at + HISTORY - self.history_len) % HISTORY;
+        for i in 0..self.history_len {
+            f.history[i] = self.history[(first + i) % HISTORY];
+        }
+        f
+    }
+}
@@ -0,0 +1,134 @@
+//! Host-independent controls. Loudness in LUFS, gains in dB, amounts in percent.
+use serde::{Deserialize, Serialize};
+
+pub const TARGET_MIN: f32 = -40.;
+pub const TARGET_MAX: f32 = 0.;
+pub const RANGE_MAX: f32 = 24.;
+/// Lowest frequency the measurement can start from. At or under this the measurement hears
+/// the full band.
+pub const FROM_MIN: f32 = 20.;
+pub const FROM_MAX: f32 = 300.;
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
+pub enum Source {
+    /// Note starts are detected from the incoming bass.
+    #[default]
+    Audio,
+    /// Note starts come from MIDI note input.
+    Midi,
+}
+
+/// Where one leveled part ends and the next begins.
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
+pub enum Segment {
+    /// Every note start.
+    Notes,
+    /// Every line of the host's beat grid, so a patch change on the same note counts too.
+    /// The default: a switch-up lands on the grid, and the grid needs no note tracking.
+    #[default]
+    Grid,
+}
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
+pub enum Grid {
+    Bar,
+    Half,
+    #[default]
+    Quarter,
+    Eighth,
+    Sixteenth,
+}
+impl Grid {
+    pub const ALL: [Grid; 5] = [
+        Grid::Bar,
+        Grid::Half,
+        Grid::Quarter,
+        Grid::Eighth,
+        Grid::Sixteenth,
+    ];
+    /// Length in quarter notes.
+    pub fn quarters(self) -> f64 {
+        match self {
+            Grid::Bar => 4.,
+            Grid::Half => 2.,
+            Grid::Quarter => 1.,
+            Grid::Eighth => 0.5,
+            Grid::Sixteenth => 0.25,
+        }
+    }
+    pub fn label(self) -> &'static str {
+        match self {
+            Grid::Bar => "1 BAR",
+            Grid::Half => "1/2",
+            Grid::Quarter => "1/4",
+            Grid::Eighth => "1/8",
+            Grid::Sixteenth => "1/16",
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq)]
+#[serde(deny_unknown_fields)]
+pub struct Settings {
+    pub source: Source,
+    pub segment: Segment,
+    pub grid: Grid,
+    /// Loudness every part should land at, measured over its first 100 ms.
+    pub target: f32,
+    /// Share of the correction that is applied.
+    pub amount: f32,
+    /// Most boost or cut, in dB.
+    pub range: f32,
+    /// The measurement hears only what is above this frequency; the gain still applies to
+    /// the full band. Set it to Anvil's Split when Anvil makes the sub.
+    pub from: f32,
+    /// Note-start threshold (Audio source), and the loudness under which a part keeps the
+    /// last gain instead of being lifted.
+    pub gate: f32,
+    pub output: f32,
+    pub bypass: bool,
+}
+impl Default for Settings {
+    fn default() -> Self {
+        Self {
+            source: Source::Audio,
+            segment: Segment::Grid,
+            grid: Grid::Quarter,
+            target: -14.,
+            amount: 100.,
+            range: 12.,
+            from: FROM_MIN,
+            gate: -48.,
+            output: 0.,
+            bypass: false,
+        }
+    }
+}
+impl Settings {
+    pub fn validate(&self) -> Result<(), &'static str> {
+        let finite = [
+            self.target,
+            self.amount,
+            self.range,
+            self.from,
+            self.gate,
+            self.output,
+        ]
+        .iter()
+        .all(|v| v.is_finite());
+        if !finite {
+            return Err("non-finite setting");
+        }
+        let ok = (TARGET_MIN..=TARGET_MAX).contains(&self.target)
+            && (0.0..=100.).contains(&self.amount)
+            && (0.0..=RANGE_MAX).contains(&self.range)
+            && (FROM_MIN..=FROM_MAX).contains(&self.from)
+            && (-60.0..=-20.).contains(&self.gate)
+            && (-12.0..=12.).contains(&self.output);
+        if ok {
+            Ok(())
+        } else {
+            Err("setting out of range")
+        }
+    }
+}
@@ -0,0 +1,334 @@
+use ballast_core::{part_gain, Engine, Grid, Segment, Settings, Source, RAMP_MS, WINDOW_MS};
+use common_dsp::loudness::{lufs, KWeighting};
+use std::f64::consts::TAU;
+
+const RATE: f32 = 48000.;
+const BPM: f64 = 120.;
+/// One quarter at 120 BPM.
+const QUARTER: usize = 24000;
+
+/// Two patches a switch-up might alternate: a loud saw and a quiet sine, an octave apart.
+fn patch(i: usize, which: usize) -> f32 {
+    let t = i as f64 / RATE as f64;
+    if which.is_multiple_of(2) {
+        let phase = (55. * t).fract();
+        (0.5 * (2. * phase - 1.)) as f32
+    } else {
+        (0.1 * (TAU * 110. * t).sin()) as f32
+    }
+}
+fn grid_engine(s: Settings) -> Engine {
+    let mut e = Engine::new(RATE, 2).unwrap();
+    e.set_settings(Settings {
+        segment: Segment::Grid,
+        grid: Grid::Quarter,
+        ..s
+    })
+    .unwrap();
+    e
+}
+/// Runs `input` through the engine in 512-sample blocks with the transport playing from 0.
+fn run(e: &mut Engine, input: &[f32]) -> Vec<f32> {
+    let mut out = Vec::with_capacity(input.len());
+    for (i, &v) in input.iter().enumerate() {
+        if i % 512 == 0 {
+            e.set_transport(Some(BPM), Some(i as f64 / RATE as f64 * BPM / 60.));
+        }
+        out.push(e.process_sample([v, v])[0]);
+    }
+    out
+}
+/// K-weighted loudness of both channels (the same signal) over `window` samples from `start`.
+fn loudness(x: &[f32], start: usize, window: usize) -> f32 {
+    let mut k = KWeighting::new(RATE);
+    // Settle the filter on what came before, as the engine's own measurement does.
+    for &v in &x[start.saturating_sub(4800)..start] {
+        k.process(v);
+    }
+    let sum: f64 = x[start..start + window]
+        .iter()
+        .map(|&v| (k.process(v) as f64).powi(2))
+        .sum();
+    lufs(2. * sum / window as f64)
+}
+fn window() -> usize {
+    (RATE * WINDOW_MS * 0.001) as usize
+}
+
+#[test]
+fn every_part_lands_at_the_target() {
+    let target = -18.;
+    let mut e = grid_engine(Settings {
+        target,
+        ..Settings::default()
+    });
+    let latency = e.latency_samples() as usize;
+    let parts = 10;
+    let input: Vec<f32> = (0..parts * QUARTER + latency)
+        .map(|i| patch(i, i / QUARTER))
+        .collect();
+    let out = run(&mut e, &input);
+    for p in 2..parts {
+        let start = p * QUARTER;
+        let before = loudness(&input, start, window());
+        let after = loudness(&out, start + latency, window());
+        assert!(
+            (after - target).abs() < 0.3,
+            "part {p}: {before:.1} → {after:.1}"
+        );
+    }
+    let f = e.take_analyzer();
+    assert!(f.spread_in > 5., "{}", f.spread_in);
+    assert!(f.spread_out < 0.1, "{}", f.spread_out);
+}
+
+#[test]
+fn the_gain_holds_still_inside_a_part_and_is_in_place_on_its_attack() {
+    let mut e = grid_engine(Settings {
+        target: -18.,
+        ..Settings::default()
+    });
+    let latency = e.latency_samples() as usize;
+    let ramp = (RATE * RAMP_MS * 0.001) as usize;
+    let input: Vec<f32> = (0..6 * QUARTER + latency)
+        .map(|i| patch(i, i / QUARTER) + 0.2)
+        .collect();
+    let out = run(&mut e, &input);
+    for p in 2..5 {
+        let start = p * QUARTER;
+        assert!(input[start].abs() > 0.05);
+        let gain = out[start + latency] / input[start];
+        for n in start..start + QUARTER - ramp {
+            if input[n].abs() < 0.05 {
+                continue;
+            }
+            let g = out[n + latency] / input[n];
+            assert!(
+                (g / gain - 1.).abs() < 1e-4,
+                "part {p}, sample {n}: {g} vs {gain}"
+            );
+        }
+    }
+}
+
+#[test]
+fn note_starts_from_the_audio_cut_the_parts() {
+    let target = -18.;
+    let mut e = Engine::new(RATE, 2).unwrap();
+    e.set_settings(Settings {
+        target,
+        segment: Segment::Notes,
+        ..Settings::default()
+    })
+    .unwrap();
+    let latency = e.latency_samples() as usize;
+    // 300 ms notes with 100 ms gaps, alternating the two patches.
+    let note = 19200;
+    let input: Vec<f32> = (0..8 * note + latency)
+        .map(|i| {
+            if i % note < 14400 && i < 8 * note {
+                patch(i, i / note)
+            } else {
+                0.
+            }
+        })
+        .collect();
+    let out = run(&mut e, &input);
+    let f = e.take_analyzer();
+    let parts = f.history[..f.count].iter().filter(|p| !p.gated).count();
+    assert_eq!(parts, 8, "{:?}", &f.history[..f.count]);
+    for n in 2..8 {
+        // The tracker finds the start a few milliseconds in; measure past that.
+        let start = n * note + 960;
+        let after = loudness(&out, start + latency, window());
+        assert!((after - target).abs() < 0.5, "note {n}: {after:.1}");
+    }
+}
+
+#[test]
+fn midi_note_starts_cut_legato_parts() {
+    let target = -18.;
+    let mut e = Engine::new(RATE, 2).unwrap();
+    e.set_settings(Settings {
+        target,
+        source: Source::Midi,
+        segment: Segment::Notes,
+        ..Settings::default()
+    })
+    .unwrap();
+    let latency = e.latency_samples() as usize;
+    let note = QUARTER;
+    let mut out = Vec::new();
+    let input: Vec<f32> = (0..6 * note + latency)
+        .map(|i| patch(i, i / note))
+        .collect();
+    for (i, &v) in input.iter().enumerate() {
+        if i % note == 0 {
+            // Legato: the new note starts before the old one ends, on the same pitch.
+            e.note_on(33);
+            if i > 0 {
+                e.note_off(33);
+                e.note_on(33);
+            }
+        }
+        out.push(e.process_sample([v, v])[0]);
+    }
+    for n in 2..6 {
+        let after = loudness(&out, n * note + latency, window());
+        assert!((after - target).abs() < 0.3, "note {n}: {after:.1}");
+    }
+}
+
+#[test]
+fn quiet_parts_keep_the_last_gain() {
+    let mut e = grid_engine(Settings {
+        target: -18.,
+        gate: -40.,
+        ..Settings::default()
+    });
+    // A loud part, then a part far under the gate, then the loud patch again. The parts change
+    // on zero crossings of a 110 Hz sine, so no step rings into the quiet part.
+    let input: Vec<f32> = (0..4 * QUARTER)
+        .map(|i| {
+            let v = 0.5 * (TAU * 110. * i as f64 / RATE as f64).sin() as f32;
+            if i / QUARTER == 2 {
+                v * 0.001
+            } else {
+                v
+            }
+        })
+        .collect();
+    run(&mut e, &input);
+    let f = e.take_analyzer();
+    let parts = &f.history[..f.count];
+    // The first part is the silence before the input reaches the measurement.
+    let quiet = 1 + parts[1..]
+        .iter()
+        .position(|p| p.gated)
+        .expect("a gated part");
+    assert_eq!(parts[quiet].gain, parts[quiet - 1].gain);
+}
+
+#[test]
+fn amount_and_range_scale_the_correction() {
+    assert_eq!(part_gain(-10., -14., 1., 12.), -4.);
+    assert_eq!(part_gain(-10., -14., 0.5, 12.), -2.);
+    assert_eq!(part_gain(-40., -14., 1., 12.), 12.);
+    assert_eq!(part_gain(0., -14., 1., 6.), -6.);
+    let mut e = grid_engine(Settings {
+        target: -18.,
+        amount: 50.,
+        ..Settings::default()
+    });
+    let input: Vec<f32> = (0..4 * QUARTER).map(|i| patch(i, i / QUARTER)).collect();
+    run(&mut e, &input);
+    let f = e.take_analyzer();
+    for p in &f.history[1..f.count] {
+        let full = -18. - p.loudness;
+        assert!((p.gain - 0.5 * full).abs() < 1e-3, "{p:?}");
+    }
+}
+
+#[test]
+fn learn_takes_the_next_part_as_the_target() {
+    let mut e = grid_engine(Settings::default());
+    let input: Vec<f32> = (0..3 * QUARTER).map(|i| patch(i, i / QUARTER)).collect();
+    run(&mut e, &input[..QUARTER + 100]);
+    e.learn();
+    assert!(e.take_analyzer().learning);
+    let before = e.take_analyzer().learn_id;
+    run(&mut e, &input[QUARTER + 100..]);
+    let f = e.take_analyzer();
+    assert!(!f.learning);
+    assert_ne!(f.learn_id, before);
+    let taken = f.history[..f.count]
+        .iter()
+        .find(|p| p.loudness == f.learned)
+        .expect("learned a part's loudness");
+    assert!(!taken.gated);
+}
+
+#[test]
+fn the_measurement_can_leave_out_the_sub() {
+    // The same top, once with a loud sub under it.
+    let top = |i: usize| (0.05 * (TAU * 1000. * i as f64 / RATE as f64).sin()) as f32;
+    let sub = |i: usize| (0.5 * (TAU * 50. * i as f64 / RATE as f64).sin()) as f32;
+    let gains = |from: f32| {
+        let mut e = grid_engine(Settings {
+            target: -24.,
+            range: 24.,
+            from,
+            ..Settings::default()
+        });
+        let input: Vec<f32> = (0..4 * QUARTER)
+            .map(|i| {
+                top(i)
+                    + if (i / QUARTER).is_multiple_of(2) {
+                        sub(i)
+                    } else {
+                        0.
+                    }
+            })
+            .collect();
+        run(&mut e, &input);
+        let f = e.take_analyzer();
+        let p = &f.history[..f.count];
+        (p[p.len() - 2].gain - p[p.len() - 1].gain).abs()
+    };
+    assert!(gains(20.) > 10.);
+    assert!(gains(200.) < 1., "{}", gains(200.));
+}
+
+#[test]
+fn bypass_is_the_input_delayed_by_the_latency() {
+    let mut e = grid_engine(Settings {
+        bypass: true,
+        target: -30.,
+        ..Settings::default()
+    });
+    let latency = e.latency_samples() as usize;
+    let lookahead = latency - window() - (RATE * RAMP_MS * 0.001) as usize;
+    // The tracker's lookahead: two periods of 30 Hz and a margin, about 67 ms.
+    assert!((lookahead as f32 / RATE - 0.067).abs() < 0.005);
+    let input: Vec<f32> = (0..2 * QUARTER).map(|i| patch(i, i / QUARTER)).collect();
+    let out = run(&mut e, &input);
+    for i in latency..input.len() {
+        assert_eq!(out[i], input[i - latency]);
+    }
+}
+
+#[test]
+fn settings_are_validated_and_serialise() {
+    assert!(Settings::default().validate().is_ok());
+    for bad in [
+        Settings {
+            target: 3.,
+            ..Settings::default()
+        },
+        Settings {
+            range: 30.,
+            ..Settings::default()
+        },
+        Settings {
+            from: 10.,
+            ..Settings::default()
+        },
+        Settings {
+            amount: f32::NAN,
+            ..Settings::default()
+        },
+    ] {
+        assert!(bad.validate().is_err());
+        assert!(Engine::new(RATE, 2).unwrap().set_settings(bad).is_err());
+    }
+    let s = Settings {
+        segment: Segment::Grid,
+        grid: Grid::Eighth,
+        source: Source::Midi,
+        target: -9.,
+        ..Settings::default()
+    };
+    let json = serde_json::to_string(&s).unwrap();
+    assert_eq!(serde_json::from_str::<Settings>(&json).unwrap(), s);
+    assert!(serde_json::from_str::<Settings>(r#"{"target":0,"oops":1}"#).is_err());
+}
@@ -0,0 +1,86 @@
+use ballast_core::{Engine, Grid, Segment, Settings, Source};
+use std::{
+    alloc::{GlobalAlloc, Layout, System},
+    cell::Cell,
+};
+
+struct CheckedAllocator;
+thread_local! {
+    static CHECK:Cell<bool>=const {Cell::new(false)};
+    static OPERATIONS:Cell<usize>=const {Cell::new(0)};
+}
+fn record() {
+    if CHECK.try_with(Cell::get).unwrap_or(false) {
+        let _ = OPERATIONS.try_with(|n| n.set(n.get() + 1));
+    }
+}
+unsafe impl GlobalAlloc for CheckedAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        record();
+        unsafe { System.alloc(layout) }
+    }
+    unsafe fn dealloc(&self, pointer: *mut u8, layout: Layout) {
+        record();
+        unsafe { System.dealloc(pointer, layout) }
+    }
+    unsafe fn realloc(&self, pointer: *mut u8, layout: Layout, size: usize) -> *mut u8 {
+        record();
+        unsafe { System.realloc(pointer, layout, size) }
+    }
+}
+#[global_allocator]
+static ALLOCATOR: CheckedAllocator = CheckedAllocator;
+
+#[test]
+fn processing_notes_settings_transport_and_analysis_do_not_allocate_or_free() {
+    let mut engine = Engine::new(48000., 2).unwrap();
+    let mut settings = Settings::default();
+    engine.set_settings(settings).unwrap();
+    CHECK.with(|v| v.set(true));
+    for i in 0..96000 {
+        if i % 512 == 0 {
+            let playing = (i / 24000) % 2 == 0;
+            engine.set_transport(
+                Some(140.),
+                playing.then_some(i as f64 / 48000. * 140. / 60.),
+            );
+        }
+        if i % 4800 == 0 {
+            let step = i / 4800;
+            settings.segment = if step % 2 == 0 {
+                Segment::Grid
+            } else {
+                Segment::Notes
+            };
+            settings.grid = Grid::ALL[step % Grid::ALL.len()];
+            settings.source = if step % 4 < 2 {
+                Source::Audio
+            } else {
+                Source::Midi
+            };
+            settings.from = 20. + 30. * (step % 5) as f32;
+            settings.bypass = step % 7 == 6;
+            engine.set_settings(settings).unwrap();
+            engine.note_on(33 + (step % 12) as u8);
+            if step % 3 == 0 {
+                engine.learn();
+            }
+        }
+        if i % 4800 == 2400 {
+            engine.note_off(33 + (i / 4800 % 12) as u8);
+        }
+        let t = i as f32 / 48000.;
+        let x = if (i / 2400) % 2 == 0 {
+            (std::f32::consts::TAU * 55. * t).sin() * 0.5
+        } else {
+            0.
+        };
+        std::hint::black_box(engine.process_sample([x, -x]));
+        if i % 1600 == 0 {
+            std::hint::black_box(engine.take_analyzer());
+        }
+    }
+    engine.reset();
+    CHECK.with(|v| v.set(false));
+    assert_eq!(OPERATIONS.with(Cell::get), 0);
+}
@@ -0,0 +1,25 @@
+[package]
+name = "ballast"
+version = "0.2.0"
+edition = "2021"
+license = "ISC"
+
+[workspace]
+
+[lib]
+crate-type = ["cdylib", "rlib"]
+
+[dependencies]
+nih_plug = { git = "https://github.com/robbert-vdh/nih-plug.git", rev = "de421011f41a6d10fc8c7a6084e4f4dee0143683", default-features = false }
+nih_plug_egui = { git = "https://github.com/robbert-vdh/nih-plug.git", rev = "de421011f41a6d10fc8c7a6084e4f4dee0143683" }
+ballast-core = { path = "../core" }
+ballast-ui = { path = "../ui" }
+crossbeam-queue = "0.3"
+
+[dev-dependencies]
+clap-sys = { git = "https://github.com/micahrj/clap-sys.git", rev = "25d7f53fdb6363ad63fbd80049cb7a42a97ac156" }
+serde_json = "1"
+
+[profile.release]
+lto = "thin"
+strip = "symbols"
@@ -0,0 +1,210 @@
+//! CLAP audio effect. All DSP state is owned by the processing thread.
+mod params;
+use ballast_core::{AnalyzerFrame, Engine};
+use crossbeam_queue::ArrayQueue;
+use nih_plug::prelude::*;
+use nih_plug_egui::{create_egui_editor, egui};
+use params::{BallastParams, FLOATS};
+use std::sync::{
+    atomic::{AtomicBool, Ordering},
+    Arc,
+};
+
+struct Shared {
+    analyzer: ArrayQueue<AnalyzerFrame>,
+    /// Set by the editor's Learn button, taken by the audio thread.
+    learn: AtomicBool,
+}
+
+struct EditorData {
+    ui: ballast_ui::State,
+    gestures: [bool; FLOATS],
+}
+pub struct Ballast {
+    params: Arc<BallastParams>,
+    shared: Arc<Shared>,
+    engine: Option<Engine>,
+    publish_count: usize,
+    publish_interval: usize,
+}
+impl Default for Ballast {
+    fn default() -> Self {
+        Self {
+            params: Arc::new(BallastParams::default()),
+            shared: Arc::new(Shared {
+                analyzer: ArrayQueue::new(2),
+                learn: AtomicBool::new(false),
+            }),
+            engine: None,
+            publish_count: 0,
+            publish_interval: 1600,
+        }
+    }
+}
+impl Plugin for Ballast {
+    const NAME: &'static str = "Ballast";
+    const VENDOR: &'static str = "Bass Foundry";
+    const URL: &'static str = "";
+    const EMAIL: &'static str = "";
+    const VERSION: &'static str = env!("CARGO_PKG_VERSION");
+    const AUDIO_IO_LAYOUTS: &'static [AudioIOLayout] = &[
+        AudioIOLayout {
+            main_input_channels: NonZeroU32::new(2),
+            main_output_channels: NonZeroU32::new(2),
+            ..AudioIOLayout::const_default()
+        },
+        AudioIOLayout {
+            main_input_channels: NonZeroU32::new(1),
+            main_output_channels: NonZeroU32::new(1),
+            ..AudioIOLayout::const_default()
+        },
+    ];
+    const MIDI_INPUT: MidiConfig = MidiConfig::Basic;
+    const SAMPLE_ACCURATE_AUTOMATION: bool = false;
+    type SysExMessage = ();
+    type BackgroundTask = ();
+    fn params(&self) -> Arc<dyn Params> {
+        self.params.clone()
+    }
+    fn editor(&mut self, _: AsyncExecutor<Self>) -> Option<Box<dyn Editor>> {
+        let params = self.params.clone();
+        let shared = self.shared.clone();
+        create_egui_editor(
+            params.editor.clone(),
+            EditorData {
+                ui: ballast_ui::State::default(),
+                gestures: [false; FLOATS],
+            },
+            |ctx, _| ballast_ui::style(ctx),
+            move |ctx, setter, data| {
+                while let Some(frame) = shared.analyzer.pop() {
+                    data.ui.accept_frame(frame);
+                }
+                let before = params.settings();
+                let mut edited = before;
+                nih_plug_egui::resizable_window::ResizableWindow::new("ballast-editor")
+                    .min_size(egui::vec2(
+                        ballast_ui::WIDTH as f32 - 80.,
+                        ballast_ui::HEIGHT as f32 - 40.,
+                    ))
+                    .show(ctx, &params.editor, |ui| {
+                        ballast_ui::show(ui, &mut edited, &mut data.ui)
+                    });
+                params.apply(
+                    setter,
+                    &before,
+                    &edited,
+                    data.ui.gesture_active,
+                    &mut data.gestures,
+                );
+                if std::mem::take(&mut data.ui.learn_request) {
+                    shared.learn.store(true, Ordering::Release);
+                }
+                ctx.request_repaint_after(std::time::Duration::from_millis(40));
+            },
+        )
+    }
+    fn initialize(
+        &mut self,
+        layout: &AudioIOLayout,
+        config: &BufferConfig,
+        context: &mut impl InitContext<Self>,
+    ) -> bool {
+        let Ok(mut engine) = Engine::new(
+            config.sample_rate,
+            layout.main_input_channels.map_or(0, |v| v.get() as usize),
+        ) else {
+            return false;
+        };
+        let settings = self.params.settings();
+        if engine.set_settings(settings).is_err() {
+            return false;
+        }
+        context.set_latency_samples(engine.latency_samples());
+        self.publish_interval = (config.sample_rate / 30.) as usize;
+        self.engine = Some(engine);
+        true
+    }
+    fn reset(&mut self) {
+        if let Some(e) = self.engine.as_mut() {
+            e.reset();
+        }
+        self.publish_count = 0;
+    }
+    fn process(
+        &mut self,
+        buffer: &mut Buffer,
+        _: &mut AuxiliaryBuffers,
+        context: &mut impl ProcessContext<Self>,
+    ) -> ProcessStatus {
+        let Some(engine) = self.engine.as_mut() else {
+            return ProcessStatus::Normal;
+        };
+        let settings = self.params.settings();
+        let _ = engine.set_settings(settings);
+        if self.shared.learn.swap(false, Ordering::AcqRel) {
+            engine.learn();
+        }
+        let transport = context.transport();
+        engine.set_transport(
+            transport.tempo,
+            if transport.playing {
+                transport.pos_beats()
+            } else {
+                None
+            },
+        );
+        let mut next = context.next_event();
+        for (index, mut sample) in buffer.iter_samples().enumerate() {
+            while let Some(event) = next {
+                if event.timing() as usize > index {
+                    break;
+                }
+                match event {
+                    NoteEvent::NoteOn { note, velocity, .. } if velocity > 0. => {
+                        engine.note_on(note)
+                    }
+                    NoteEvent::NoteOn { note, .. } | NoteEvent::NoteOff { note, .. } => {
+                        engine.note_off(note)
+                    }
+                    NoteEvent::Choke { note, .. } => engine.note_off(note),
+                    _ => {}
+                }
+                next = context.next_event();
+            }
+            let x = [
+                *sample.get_mut(0).unwrap(),
+                if engine.channels() == 2 {
+                    *sample.get_mut(1).unwrap()
+                } else {
+                    0.
+                },
+            ];
+            let out = engine.process_sample(x);
+            for (c, value) in sample.into_iter().enumerate() {
+                *value = out[c];
+            }
+            self.publish_count += 1;
+            if self.publish_count >= self.publish_interval {
+                let _ = self.shared.analyzer.force_push(engine.take_analyzer());
+                self.publish_count = 0;
+            }
+        }
+        // The lookahead delay must drain after input stops.
+        ProcessStatus::KeepAlive
+    }
+}
+impl ClapPlugin for Ballast {
+    const CLAP_ID: &'static str = "io.narl.bass-foundry.ballast";
+    const CLAP_DESCRIPTION: Option<&'static str> =
+        Some("Levels every note or switch-up to one loudness with a single gain each");
+    const CLAP_MANUAL_URL: Option<&'static str> = None;
+    const CLAP_SUPPORT_URL: Option<&'static str> = None;
+    const CLAP_FEATURES: &'static [ClapFeature] = &[
+        ClapFeature::AudioEffect,
+        ClapFeature::Utility,
+        ClapFeature::Stereo,
+        ClapFeature::Mono,
+    ];
+}
+nih_export_clap!(Ballast);
@@ -0,0 +1,203 @@
+use ballast_core::{
+    Grid, Segment, Settings, Source, FROM_MAX, FROM_MIN, RANGE_MAX, TARGET_MAX, TARGET_MIN,
+};
+use nih_plug::prelude::*;
+use nih_plug_egui::EguiState;
+use std::sync::Arc;
+
+#[derive(Enum, Debug, PartialEq, Eq, Clone, Copy)]
+pub enum SourceParam {
+    #[id = "audio"]
+    Audio,
+    #[id = "midi"]
+    #[name = "MIDI"]
+    Midi,
+}
+#[derive(Enum, Debug, PartialEq, Eq, Clone, Copy)]
+pub enum SegmentParam {
+    #[id = "notes"]
+    Notes,
+    #[id = "grid"]
+    Grid,
+}
+#[derive(Enum, Debug, PartialEq, Eq, Clone, Copy)]
+pub enum GridParam {
+    #[id = "bar"]
+    #[name = "1 bar"]
+    Bar,
+    #[id = "1-2"]
+    #[name = "1/2"]
+    Half,
+    #[id = "1-4"]
+    #[name = "1/4"]
+    Quarter,
+    #[id = "1-8"]
+    #[name = "1/8"]
+    Eighth,
+    #[id = "1-16"]
+    #[name = "1/16"]
+    Sixteenth,
+}
+const GRIDS: [(GridParam, Grid); 5] = [
+    (GridParam::Bar, Grid::Bar),
+    (GridParam::Half, Grid::Half),
+    (GridParam::Quarter, Grid::Quarter),
+    (GridParam::Eighth, Grid::Eighth),
+    (GridParam::Sixteenth, Grid::Sixteenth),
+];
+fn grid_param(g: Grid) -> GridParam {
+    GRIDS
+        .iter()
+        .find(|(_, v)| *v == g)
+        .map_or(GridParam::Quarter, |(p, _)| *p)
+}
+fn linear(name: &str, v: f32, min: f32, max: f32, unit: &'static str) -> FloatParam {
+    FloatParam::new(name, v, FloatRange::Linear { min, max }).with_unit(unit)
+}
+/// Continuous controls, in the order of the gesture slots.
+pub const FLOATS: usize = 6;
+
+#[derive(Params)]
+pub struct BallastParams {
+    #[persist = "editor"]
+    pub editor: Arc<EguiState>,
+    #[id = "source"]
+    pub source: EnumParam<SourceParam>,
+    #[id = "segment"]
+    pub segment: EnumParam<SegmentParam>,
+    #[id = "grid"]
+    pub grid: EnumParam<GridParam>,
+    #[id = "target"]
+    pub target: FloatParam,
+    #[id = "amount"]
+    pub amount: FloatParam,
+    #[id = "range"]
+    pub range: FloatParam,
+    #[id = "from"]
+    pub from: FloatParam,
+    #[id = "gate"]
+    pub gate: FloatParam,
+    #[id = "output"]
+    pub output: FloatParam,
+    #[id = "bypass"]
+    pub bypass: BoolParam,
+}
+impl Default for BallastParams {
+    fn default() -> Self {
+        let d = Settings::default();
+        Self {
+            editor: EguiState::from_size(ballast_ui::WIDTH, ballast_ui::HEIGHT),
+            source: EnumParam::new("Note source", SourceParam::Audio),
+            segment: EnumParam::new("Parts from", SegmentParam::Grid),
+            grid: EnumParam::new("Grid", grid_param(d.grid)),
+            target: linear("Target", d.target, TARGET_MIN, TARGET_MAX, " LUFS"),
+            amount: linear("Amount", d.amount, 0., 100., " %"),
+            range: linear("Range", d.range, 0., RANGE_MAX, " dB"),
+            from: FloatParam::new(
+                "Measure from",
+                d.from,
+                FloatRange::Skewed {
+                    min: FROM_MIN,
+                    max: FROM_MAX,
+                    factor: FloatRange::skew_factor(-1.),
+                },
+            )
+            .with_unit(" Hz"),
+            gate: linear("Gate", d.gate, -60., -20., " dB"),
+            output: linear("Output", d.output, -12., 12., " dB"),
+            bypass: BoolParam::new("Bypass", false).make_bypass(),
+        }
+    }
+}
+impl BallastParams {
+    pub fn settings(&self) -> Settings {
+        let grid = self.grid.value();
+        Settings {
+            source: match self.source.value() {
+                SourceParam::Audio => Source::Audio,
+                SourceParam::Midi => Source::Midi,
+            },
+            segment: match self.segment.value() {
+                SegmentParam::Notes => Segment::Notes,
+                SegmentParam::Grid => Segment::Grid,
+            },
+            grid: GRIDS
+                .iter()
+                .find(|(p, _)| *p == grid)
+                .map_or(Grid::Quarter, |(_, g)| *g),
+            target: self.target.value(),
+            amount: self.amount.value(),
+            range: self.range.value(),
+            from: self.from.value(),
+            gate: self.gate.value(),
+            output: self.output.value(),
+            bypass: self.bypass.value(),
+        }
+    }
+    fn floats(&self) -> [&FloatParam; FLOATS] {
+        [
+            &self.target,
+            &self.amount,
+            &self.range,
+            &self.from,
+            &self.gate,
+            &self.output,
+        ]
+    }
+    fn values(s: &Settings) -> [f32; FLOATS] {
+        [s.target, s.amount, s.range, s.from, s.gate, s.output]
+    }
+    /// Pushes every changed editor value to the host. Continuous controls hold one gesture
+    /// while the pointer is down; switches are set in a single gesture.
+    pub fn apply(
+        &self,
+        setter: &ParamSetter,
+        old: &Settings,
+        new: &Settings,
+        dragging: bool,
+        open: &mut [bool; FLOATS],
+    ) {
+        let pairs = Self::values(old).into_iter().zip(Self::values(new));
+        for (i, (p, (a, b))) in self.floats().into_iter().zip(pairs).enumerate() {
+            if a != b {
+                if !open[i] {
+                    open[i] = true;
+                    setter.begin_set_parameter(p);
+                }
+                setter.set_parameter(p, b);
+            }
+            if !dragging && open[i] {
+                setter.end_set_parameter(p);
+                open[i] = false;
+            }
+        }
+        if new.bypass != old.bypass {
+            setter.begin_set_parameter(&self.bypass);
+            setter.set_parameter(&self.bypass, new.bypass);
+            setter.end_set_parameter(&self.bypass);
+        }
+        if new.source != old.source {
+            let v = match new.source {
+                Source::Audio => SourceParam::Audio,
+                Source::Midi => SourceParam::Midi,
+            };
+            setter.begin_set_parameter(&self.source);
+            setter.set_parameter(&self.source, v);
+            setter.end_set_parameter(&self.source);
+        }
+        if new.segment != old.segment {
+            let v = match new.segment {
+                Segment::Notes => SegmentParam::Notes,
+                Segment::Grid => SegmentParam::Grid,
+            };
+            setter.begin_set_parameter(&self.segment);
+            setter.set_parameter(&self.segment, v);
+            setter.end_set_parameter(&self.segment);
+        }
+        if new.grid != old.grid {
+            setter.begin_set_parameter(&self.grid);
+            setter.set_parameter(&self.grid, grid_param(new.grid));
+            setter.end_set_parameter(&self.grid);
+        }
+    }
+}
@@ -0,0 +1,216 @@
+//! Exercise the actual exported CLAP ABI without requiring a GUI or installed DAW.
+use clap_sys::{
+    audio_buffer::*,
+    events::*,
+    ext::{audio_ports::*, latency::*, state::*},
+    factory::plugin_factory::*,
+    host::*,
+    process::*,
+    stream::*,
+    version::*,
+};
+use std::{
+    ffi::{c_char, c_void, CStr},
+    io::{Cursor, Read},
+    ptr,
+};
+
+unsafe extern "C" fn extension(_: *const clap_host, _: *const c_char) -> *const c_void {
+    ptr::null()
+}
+unsafe extern "C" fn request(_: *const clap_host) {}
+unsafe extern "C" fn count(_: *const clap_input_events) -> u32 {
+    0
+}
+unsafe extern "C" fn event(_: *const clap_input_events, _: u32) -> *const clap_event_header {
+    ptr::null()
+}
+unsafe extern "C" fn push(_: *const clap_output_events, _: *const clap_event_header) -> bool {
+    true
+}
+unsafe extern "C" fn write(stream: *const clap_ostream, buffer: *const c_void, size: u64) -> i64 {
+    // SAFETY: The test owns the Vec for the entire synchronous save call.
+    let bytes = unsafe { &mut *((*stream).ctx as *mut Vec<u8>) };
+    bytes.extend_from_slice(unsafe {
+        std::slice::from_raw_parts(buffer as *const u8, size as usize)
+    });
+    size as i64
+}
+unsafe extern "C" fn read(stream: *const clap_istream, buffer: *mut c_void, size: u64) -> i64 {
+    // SAFETY: The test owns the Cursor; the wrapper supplies writable stream storage.
+    let cursor = unsafe { &mut *((*stream).ctx as *mut Cursor<Vec<u8>>) };
+    cursor
+        .read(unsafe { std::slice::from_raw_parts_mut(buffer as *mut u8, size as usize) })
+        .unwrap() as i64
+}
+
+#[test]
+fn effect_ports_state_latency_and_audio_lifecycle() {
+    // SAFETY: All callbacks, strings, streams, buffers, and the host outlive their
+    // synchronous ABI calls. Activation/processing/destruction follow CLAP order.
+    unsafe {
+        let entry = &ballast::clap_entry;
+        assert!(entry.init.unwrap()(c"ballast.clap".as_ptr()));
+        let factory = entry.get_factory.unwrap()(CLAP_PLUGIN_FACTORY_ID.as_ptr())
+            as *const clap_plugin_factory;
+        assert!(!factory.is_null());
+        let factory = &*factory;
+        assert_eq!(factory.get_plugin_count.unwrap()(factory), 1);
+        let descriptor = factory.get_plugin_descriptor.unwrap()(factory, 0);
+        assert!(!descriptor.is_null());
+        assert_eq!(CStr::from_ptr((*descriptor).name), c"Ballast");
+        assert_eq!(
+            CStr::from_ptr((*descriptor).id),
+            c"io.narl.bass-foundry.ballast"
+        );
+        assert!(factory.get_plugin_descriptor.unwrap()(factory, 1).is_null());
+        let host = clap_host {
+            clap_version: CLAP_VERSION,
+            host_data: ptr::null_mut(),
+            name: c"Storyboard test host".as_ptr(),
+            vendor: c"Tests".as_ptr(),
+            url: c"".as_ptr(),
+            version: c"1.0".as_ptr(),
+            get_extension: Some(extension),
+            request_restart: Some(request),
+            request_process: Some(request),
+            request_callback: Some(request),
+        };
+        let plugin = factory.create_plugin.unwrap()(factory, &host, (*descriptor).id);
+        assert!(!plugin.is_null());
+        let p = &*plugin;
+        assert!(p.init.unwrap()(plugin));
+        let ports = p.get_extension.unwrap()(plugin, CLAP_EXT_AUDIO_PORTS.as_ptr())
+            as *const clap_plugin_audio_ports;
+        assert!(!ports.is_null());
+        assert_eq!((*ports).count.unwrap()(plugin, false), 1);
+        assert_eq!((*ports).count.unwrap()(plugin, true), 1);
+        let latency = p.get_extension.unwrap()(plugin, CLAP_EXT_LATENCY.as_ptr())
+            as *const clap_plugin_latency;
+        assert!(!latency.is_null());
+        let state =
+            p.get_extension.unwrap()(plugin, CLAP_EXT_STATE.as_ptr()) as *const clap_plugin_state;
+        assert!(!state.is_null());
+        let state = &*state;
+        let save = || {
+            let mut bytes = Vec::new();
+            let stream = clap_ostream {
+                ctx: &mut bytes as *mut Vec<u8> as *mut c_void,
+                write: Some(write),
+            };
+            assert!(state.save.unwrap()(plugin, &stream));
+            bytes
+        };
+        let mut envelope: nih_plug::prelude::PluginState =
+            serde_json::from_slice(&save()[8..]).unwrap();
+        use nih_plug::wrapper::state::ParamValue;
+        // Amount 0 passes the input through the lookahead delay unchanged.
+        envelope.params.insert("amount".into(), ParamValue::F32(0.));
+        envelope
+            .params
+            .insert("target".into(), ParamValue::F32(-20.));
+        envelope.params.insert("from".into(), ParamValue::F32(100.));
+        envelope
+            .params
+            .insert("segment".into(), ParamValue::String("grid".into()));
+        envelope
+            .params
+            .insert("grid".into(), ParamValue::String("1-8".into()));
+        envelope
+            .params
+            .insert("source".into(), ParamValue::String("midi".into()));
+        let encoded = serde_json::to_vec(&envelope).unwrap();
+        let mut framed = (encoded.len() as u64).to_le_bytes().to_vec();
+        framed.extend_from_slice(&encoded);
+        let mut bytes = Cursor::new(framed);
+        let stream = clap_istream {
+            ctx: &mut bytes as *mut Cursor<Vec<u8>> as *mut c_void,
+            read: Some(read),
+        };
+        assert!(state.load.unwrap()(plugin, &stream));
+        let restored: nih_plug::prelude::PluginState =
+            serde_json::from_slice(&save()[8..]).unwrap();
+        assert_eq!(
+            serde_json::to_value(&restored.params).unwrap(),
+            serde_json::to_value(&envelope.params).unwrap()
+        );
+        for rate in [44100., 48000., 96000.] {
+            assert!(p.activate.unwrap()(plugin, rate, 1, 512));
+            let delay = (*latency).get.unwrap()(plugin) as usize;
+            // The tracker's 67 ms, the 100 ms measuring window and the 5 ms ramp.
+            assert!((delay as f64 / rate - 0.172).abs() < 0.005, "{delay}");
+            assert!(p.start_processing.unwrap()(plugin));
+            let total = delay + 9600;
+            let mut position = 0;
+            let (mut energy_in, mut energy_out) = (0f64, 0f64);
+            while position < total {
+                let frames = [1, 127, 512, 31][position % 4].min(total - position);
+                // A 1 kHz tone at amount 0.
+                let tone = |n: usize| {
+                    0.25 * (std::f64::consts::TAU * 1000. * n as f64 / rate).sin() as f32
+                };
+                let mut input_left = [0f32; 512];
+                let mut input_right = [0f32; 512];
+                for i in 0..frames {
+                    input_left[i] = tone(position + i);
+                    input_right[i] = -tone(position + i);
+                }
+                let mut left = [0f32; 512];
+                let mut right = [0f32; 512];
+                let mut in_channels = [input_left.as_mut_ptr(), input_right.as_mut_ptr()];
+                let mut out_channels = [left.as_mut_ptr(), right.as_mut_ptr()];
+                let incoming = clap_audio_buffer {
+                    data32: in_channels.as_mut_ptr(),
+                    data64: ptr::null_mut(),
+                    channel_count: 2,
+                    latency: 0,
+                    constant_mask: 0,
+                };
+                let mut outgoing_audio = clap_audio_buffer {
+                    data32: out_channels.as_mut_ptr(),
+                    data64: ptr::null_mut(),
+                    channel_count: 2,
+                    latency: 0,
+                    constant_mask: 0,
+                };
+                let input = clap_input_events {
+                    ctx: ptr::null_mut(),
+                    size: Some(count),
+                    get: Some(event),
+                };
+                let outgoing = clap_output_events {
+                    ctx: ptr::null_mut(),
+                    try_push: Some(push),
+                };
+                let process = clap_process {
+                    steady_time: position as i64,
+                    frames_count: frames as u32,
+                    transport: ptr::null(),
+                    audio_inputs: &incoming,
+                    audio_outputs: &mut outgoing_audio,
+                    audio_inputs_count: 1,
+                    audio_outputs_count: 1,
+                    in_events: &input,
+                    out_events: &outgoing,
+                };
+                assert_ne!(p.process.unwrap()(plugin, &process), CLAP_PROCESS_ERROR);
+                for i in 0..frames {
+                    let n = position + i;
+                    if n < delay {
+                        assert!(left[i].abs() < 1e-6, "output before the lookahead");
+                    } else if n > delay + 4800 {
+                        energy_in += (tone(n - delay) as f64).powi(2);
+                        energy_out += (left[i] as f64).powi(2) + (right[i] as f64).powi(2);
+                    }
+                }
+                position += frames;
+            }
+            let ratio_db = 10. * (energy_out / (2. * energy_in)).log10();
+            assert!(ratio_db.abs() < 0.2, "{ratio_db}");
+            p.stop_processing.unwrap()(plugin);
+            p.deactivate.unwrap()(plugin);
+        }
+        p.destroy.unwrap()(plugin);
+        entry.deinit.unwrap()();
+    }
+}
@@ -0,0 +1,11 @@
+[package]
+name = "ballast-ui"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+egui = "0.31.1"
+ballast-core = { path = "../core" }
+common-ui = { path = "../../common/ui" }
+common-dsp = { path = "../../common/dsp" }
@@ -0,0 +1,376 @@
+//! Ballast editor, shared by the CLAP wrapper and the headless renderer.
+use ballast_core::{
+    AnalyzerFrame, Grid, Segment, Settings, Source, FROM_MAX, FROM_MIN, HISTORY, RANGE_MAX,
+    TARGET_MAX, TARGET_MIN,
+};
+use common_ui::*;
+use egui::{self, Color32, FontId, Pos2, Rect, RichText, Sense, Stroke, Vec2};
+
+pub use common_ui::style;
+pub const WIDTH: u32 = 980;
+pub const HEIGHT: u32 = 660;
+
+pub struct State {
+    pub analyzer: AnalyzerFrame,
+    /// Set by the Learn button; the wrapper passes it to the engine and clears it.
+    pub learn_request: bool,
+    /// The last Learn result already applied. None until the first frame arrives, so an old
+    /// result is not applied again when the editor opens.
+    learn_seen: Option<u32>,
+    learned: Option<f32>,
+    /// True while a pointer button is held, so knob drags become one host gesture.
+    pub gesture_active: bool,
+    pub help: String,
+}
+impl Default for State {
+    fn default() -> Self {
+        Self {
+            analyzer: AnalyzerFrame::default(),
+            learn_request: false,
+            learn_seen: None,
+            learned: None,
+            gesture_active: false,
+            help: DEFAULT_HELP.into(),
+        }
+    }
+}
+const DEFAULT_HELP: &str = "Put Ballast on the bass after its sound design. Press LEARN on the \
+                            switch-up that sits right, or set Target.";
+impl State {
+    pub fn accept_frame(&mut self, frame: AnalyzerFrame) {
+        match self.learn_seen {
+            Some(id) if id != frame.learn_id && frame.learned.is_finite() => {
+                self.learned = Some(frame.learned);
+            }
+            _ => {}
+        }
+        self.learn_seen = Some(frame.learn_id);
+        self.analyzer = frame;
+    }
+}
+fn hint(r: &egui::Response, state: &mut State, text: &str) {
+    if r.hovered() || r.has_focus() {
+        state.help = text.into();
+    }
+}
+#[allow(clippy::too_many_arguments)]
+fn knob(
+    ui: &mut egui::Ui,
+    state: &mut State,
+    name: &str,
+    value: &mut f32,
+    range: std::ops::RangeInclusive<f32>,
+    default: f32,
+    unit: &str,
+    help: &str,
+) {
+    ui.vertical_centered(|ui| {
+        let r = rotary(ui, name, value, range, default, unit, 72., ACCENT);
+        hint(&r, state, help);
+    });
+}
+
+const LOW: f32 = -42.;
+const HIGH: f32 = 0.;
+
+/// The last parts: their loudness in (bars), after Ballast (marks) and the target.
+fn parts(ui: &mut egui::Ui, settings: &Settings, frame: &AnalyzerFrame, height: f32) {
+    let (rect, _) = ui.allocate_exact_size(Vec2::new(ui.available_width(), height), Sense::hover());
+    let p = ui.painter_at(rect);
+    p.rect_filled(rect, 2., SCREEN);
+    p.text(
+        rect.left_top() + Vec2::new(10., 8.),
+        egui::Align2::LEFT_TOP,
+        format!("LAST {HISTORY} PARTS · LOUDNESS OF THE FIRST 100 MS"),
+        FontId::proportional(11.),
+        MUTED,
+    );
+    p.text(
+        rect.right_top() + Vec2::new(-12., 8.),
+        egui::Align2::RIGHT_TOP,
+        "bar: in · mark: out",
+        FontId::proportional(11.),
+        MUTED,
+    );
+    let area = Rect::from_min_max(
+        rect.left_top() + Vec2::new(44., 30.),
+        rect.right_bottom() - Vec2::new(12., 12.),
+    );
+    let y = |lufs: f32| {
+        let t = ((lufs - LOW) / (HIGH - LOW)).clamp(0., 1.);
+        area.bottom() - t * area.height()
+    };
+    for db in [-36., -24., -12., 0.] {
+        p.line_segment(
+            [
+                Pos2::new(area.left(), y(db)),
+                Pos2::new(area.right(), y(db)),
+            ],
+            Stroke::new(1.0_f32, Color32::from_rgb(32, 35, 40)),
+        );
+        p.text(
+            Pos2::new(area.left() - 6., y(db)),
+            egui::Align2::RIGHT_CENTER,
+            format!("{db:.0}"),
+            FontId::monospace(10.),
+            DIM,
+        );
+    }
+    let column = area.width() / HISTORY as f32;
+    // Newest part on the right.
+    let offset = HISTORY - frame.count;
+    for i in 0..frame.count {
+        let part = frame.history[i];
+        let x = area.left() + column * (offset + i) as f32;
+        let bar = Rect::from_min_max(
+            Pos2::new(x + column * 0.2, y(part.loudness)),
+            Pos2::new(x + column * 0.8, area.bottom()),
+        );
+        let color = if part.gated {
+            DIM.gamma_multiply(0.6)
+        } else {
+            STEEL.gamma_multiply(0.45)
+        };
+        p.rect_filled(bar, 1., color);
+        if !part.gated {
+            let out = y(part.loudness + part.gain);
+            p.line_segment(
+                [
+                    Pos2::new(x + column * 0.1, out),
+                    Pos2::new(x + column * 0.9, out),
+                ],
+                Stroke::new(3.0_f32, ACCENT),
+            );
+        }
+    }
+    let t = y(settings.target);
+    p.line_segment(
+        [Pos2::new(area.left(), t), Pos2::new(area.right(), t)],
+        Stroke::new(1.0_f32, ACCENT.gamma_multiply(0.5)),
+    );
+    p.text(
+        Pos2::new(area.left() + 4., t - 3.),
+        egui::Align2::LEFT_BOTTOM,
+        format!("TARGET {:.1} LUFS", settings.target),
+        FontId::proportional(10.),
+        ACCENT,
+    );
+    p.rect_stroke(
+        rect,
+        2.,
+        Stroke::new(1.0_f32, EDGE),
+        egui::StrokeKind::Inside,
+    );
+}
+
+pub fn show(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
+    backdrop(ui);
+    state.help = DEFAULT_HELP.into();
+    state.gesture_active = ui.input(|i| i.pointer.any_down());
+    if let Some(l) = state.learned.take() {
+        settings.target = l.clamp(TARGET_MIN, TARGET_MAX);
+    }
+    ui.add_space(2.);
+    header(ui, "BALLAST", "SWITCH-UP LEVELLER", |ui| {
+        let r = ui
+            .selectable_label(settings.bypass, RichText::new("BYPASS").size(13.))
+            .on_hover_text("Crossfade to the delayed dry signal.");
+        if r.clicked() {
+            settings.bypass = !settings.bypass;
+        }
+        ui.separator();
+        if settings.segment == Segment::Notes {
+            for (source, label) in [(Source::Midi, "MIDI"), (Source::Audio, "AUDIO")] {
+                let r =
+                    ui.selectable_label(settings.source == source, RichText::new(label).size(13.));
+                if r.clicked() {
+                    settings.source = source;
+                }
+            }
+            caption(ui, "NOTES FROM");
+            ui.separator();
+        }
+        for (segment, label) in [(Segment::Grid, "GRID"), (Segment::Notes, "NOTES")] {
+            let r =
+                ui.selectable_label(settings.segment == segment, RichText::new(label).size(13.));
+            if r.clicked() {
+                settings.segment = segment;
+            }
+        }
+        caption(ui, "PARTS FROM");
+    });
+    ui.add_space(6.);
+    let frame = state.analyzer;
+    ui.horizontal_top(|ui| {
+        panel(ui, |ui| {
+            ui.set_width(250.);
+            ui.set_min_height(TOP);
+            ui.vertical(|ui| readings(ui, settings, state, &frame));
+        });
+        ui.add_space(4.);
+        panel(ui, |ui| {
+            ui.set_width(ui.available_width());
+            parts(ui, settings, &frame, TOP);
+        });
+    });
+    ui.add_space(6.);
+    panel(ui, |ui| {
+        ui.set_width(ui.available_width());
+        ui.vertical(|ui| controls(ui, settings, state));
+    });
+    ui.separator();
+    ui.label(RichText::new(&state.help).color(MUTED));
+}
+const TOP: f32 = 300.;
+
+fn readings(ui: &mut egui::Ui, settings: &Settings, state: &mut State, frame: &AnalyzerFrame) {
+    caption(ui, "SPREAD OF THE LAST PARTS");
+    let known = frame.spread_in.is_finite();
+    ui.label(
+        RichText::new(if known {
+            format!("{:.1} · {:.1} dB", frame.spread_in, frame.spread_out)
+        } else {
+            "—".into()
+        })
+        .font(FontId::new(34., egui::FontFamily::Name("medium".into())))
+        .color(if known { TEXT } else { DIM }),
+    );
+    ui.label(
+        RichText::new("in · out, standard deviation")
+            .size(12.)
+            .color(MUTED),
+    );
+    ui.add_space(12.);
+    readout(ui, "GAIN NOW", format!("{:+.1} dB", frame.gain), ACCENT);
+    readout(ui, "TARGET", format!("{:.1} LUFS", settings.target), TEXT);
+    let label = if frame.learning || state.learn_request {
+        "LISTENING"
+    } else {
+        "LEARN"
+    };
+    let r = ui.selectable_label(
+        frame.learning || state.learn_request,
+        RichText::new(label).size(13.),
+    );
+    if r.clicked() {
+        state.learn_request = true;
+    }
+    hint(
+        &r,
+        state,
+        "Takes the loudness of the next part over the gate as the target. Press it just \
+         before the switch-up that sits right in the mix.",
+    );
+    ui.add_space(10.);
+    ui.label(
+        RichText::new(format!(
+            "{:.0} ms lookahead · {}",
+            frame.latency as f32 / frame.sample_rate.max(1.) * 1000.,
+            match settings.segment {
+                Segment::Notes => match settings.source {
+                    Source::Audio => "parts at detected notes".to_string(),
+                    Source::Midi => "parts at MIDI notes".to_string(),
+                },
+                Segment::Grid => format!(
+                    "grid at {:.1} BPM, {}",
+                    frame.tempo,
+                    if frame.synced {
+                        "host transport"
+                    } else {
+                        "free running"
+                    }
+                ),
+            }
+        ))
+        .size(12.)
+        .color(MUTED),
+    );
+}
+
+fn controls(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
+    let d = Settings::default();
+    if settings.segment == Segment::Grid {
+        ui.horizontal(|ui| {
+            caption(ui, "ONE PART EVERY");
+            ui.add_space(6.);
+            for grid in Grid::ALL {
+                let r = ui
+                    .selectable_label(settings.grid == grid, RichText::new(grid.label()).size(13.));
+                if r.clicked() {
+                    settings.grid = grid;
+                }
+                hint(
+                    &r,
+                    state,
+                    "A new part starts on every line of this grid, also when the note does not \
+                     change.",
+                );
+            }
+        });
+        ui.add_space(8.);
+        ui.separator();
+    }
+    ui.columns(6, |c| {
+        knob(
+            &mut c[0],
+            state,
+            "Target",
+            &mut settings.target,
+            TARGET_MIN..=TARGET_MAX,
+            d.target,
+            " LUFS",
+            "Loudness every part lands at, over its first 100 ms.",
+        );
+        knob(
+            &mut c[1],
+            state,
+            "Amount",
+            &mut settings.amount,
+            0. ..=100.,
+            d.amount,
+            " %",
+            "Share of the correction. 50 % halves the differences between parts.",
+        );
+        knob(
+            &mut c[2],
+            state,
+            "Range",
+            &mut settings.range,
+            0. ..=RANGE_MAX,
+            d.range,
+            " dB",
+            "Most boost or cut a part gets.",
+        );
+        knob(
+            &mut c[3],
+            state,
+            "Measure from",
+            &mut settings.from,
+            FROM_MIN..=FROM_MAX,
+            d.from,
+            " Hz",
+            "The measurement hears only what is above this. Set it to Anvil's Split when \
+             Anvil makes the sub; the gain still applies to the whole signal.",
+        );
+        knob(
+            &mut c[4],
+            state,
+            "Gate",
+            &mut settings.gate,
+            -60. ..=-20.,
+            d.gate,
+            " dB",
+            "Note-start threshold, and the loudness under which a part keeps the last gain.",
+        );
+        knob(
+            &mut c[5],
+            state,
+            "Output",
+            &mut settings.output,
+            -12. ..=12.,
+            d.output,
+            " dB",
+            "Output trim.",
+        );
+    });
+}
@@ -0,0 +1,12 @@
+[package]
+name = "braze-core"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+common-dsp = { path = "../../common/dsp" }
+serde = { workspace = true }
+
+[dev-dependencies]
+serde_json = { workspace = true }
@@ -0,0 +1,358 @@
+//! Tempo-locked beating: adds a detuned copy of the bass whose beating stays in time with
+//! the track on every note.
+//!
+//! Two layers detuned by a ratio r beat at k·f0·(r − 1) on harmonic k, so a fixed detune
+//! beats at a different rate on every note. Braze sets the detune per note from the tracked
+//! fundamental: harmonic `harmonic` beats once per `rate` note value, and harmonic n beats
+//! n/harmonic times as fast, so every harmonic beats on the tempo grid.
+//!
+//! The copy is the bass read from a delay line whose delay falls by one period of the note
+//! per beat cycle of the chosen harmonic. That shifts the copy up by exactly the wanted
+//! ratio. When the delay has fallen by a whole period it jumps back by one period: for a
+//! periodic note both read positions hold the same waveform, so the jump is crossfaded over
+//! a few milliseconds without a seam. The delay is set from the host's beat position, so
+//! the beat's peaks land on the grid, not just at the right rate. At a beat peak the copy
+//! lines up with the bass exactly.
+//!
+//! Low cut removes the copy below a frequency with a 4th-order Linkwitz–Riley high-pass,
+//! so the sub does not beat. The bass is split by the same crossover; its two bands are in
+//! phase with the copy's high-pass at every frequency, so the beat peaks stay on the grid,
+//! and the loudness correction for the copy applies above the cut only, so the sub keeps
+//! its level.
+mod settings;
+use common_dsp::svf::{Svf, SvfCoef};
+use common_dsp::tracker::{PitchFollower, Tracker, TrackerConfig};
+use common_dsp::{coefficient, db_to_gain, hz_to_midi};
+pub use settings::{Rate, Settings, Source, HARMONIC_MAX, LOW_CUT_MAX, LOW_CUT_OFF};
+
+pub const MIN_HZ: f32 = TrackerConfig::BASS.min_hz;
+pub const MAX_HZ: f32 = TrackerConfig::BASS.max_hz;
+/// Fundamental the copy assumes before the first note.
+pub const FALLBACK_HZ: f32 = 55.;
+/// Tempo when the host reports none.
+pub const DEFAULT_TEMPO: f64 = 120.;
+/// Crossfade between the old and the new read position.
+const FADE_MS: f32 = 6.;
+/// A beat position that moves further than this (in cycles of the chosen harmonic) from
+/// one sample to the next counts as a jump: a locate, a loop, or a changed control.
+const JUMP: f64 = 1e-3;
+/// Pitch smoothing for bends and slides.
+const PITCH_MS: f32 = 5.;
+
+#[derive(Clone, Copy, Debug)]
+pub struct AnalyzerFrame {
+    /// Fundamental the copy is tuned to, 0 before the first note.
+    pub hz: f32,
+    /// Sounding note, rounded; None between notes.
+    pub note: Option<u8>,
+    /// Beat position at the output, in quarter notes.
+    pub beats: f64,
+    pub tempo: f64,
+    /// True when the beat position comes from the host's transport.
+    pub synced: bool,
+    /// Detune of the copy as a ratio, 1 before the first note.
+    pub ratio: f32,
+    pub latency: u32,
+    pub sample_rate: f32,
+}
+impl Default for AnalyzerFrame {
+    fn default() -> Self {
+        Self {
+            hz: 0.,
+            note: None,
+            beats: 0.,
+            tempo: DEFAULT_TEMPO,
+            synced: false,
+            ratio: 1.,
+            latency: 0,
+            sample_rate: 48000.,
+        }
+    }
+}
+
+/// Beat cycles of the chosen harmonic at `beats` quarter notes, for one channel.
+pub fn cycles(s: &Settings, beats: f64, channel: usize) -> f64 {
+    beats / s.rate.quarters() + s.phase as f64 / 360. + channel as f64 * s.width as f64 * 0.005
+}
+/// Level of harmonic `n` in the sum, against the bass alone, at `cycles` of the chosen
+/// harmonic, with the copy at `depth` (0–1). Includes the output's loudness correction.
+pub fn envelope(s: &Settings, n: u32, cycles: f64, depth: f32) -> f32 {
+    let theta = std::f64::consts::TAU * n as f64 / s.harmonic as f64 * cycles;
+    let (re, im) = (1. + depth as f64 * theta.cos(), depth as f64 * theta.sin());
+    ((re * re + im * im).sqrt() / (1. + depth as f64 * depth as f64).sqrt()) as f32
+}
+
+#[derive(Clone, Copy, Debug, Default)]
+struct Tap {
+    /// Delay in samples.
+    delay: f32,
+    /// Delay change per sample, so a fading tap keeps its course.
+    slope: f32,
+}
+
+#[derive(Clone, Copy, Debug, Default)]
+struct Channel {
+    active: Tap,
+    old: Tap,
+    /// Weight of the old tap, falling to 0.
+    fade: f32,
+    /// Whole cycles the active tap's delay is counted from.
+    whole: f64,
+    /// Beat cycle position (`cycles / harmonic + 0.5`) of the previous sample.
+    last: f64,
+    started: bool,
+    copy_high: [Svf; 2],
+    high: [Svf; 2],
+    low: [Svf; 2],
+}
+
+pub struct Engine {
+    rate: f32,
+    channels: usize,
+    settings: Settings,
+    latency: usize,
+    audio: Vec<[f32; 2]>,
+    audio_at: usize,
+    tracker: Tracker,
+    pitch: PitchFollower,
+    pitch_coef: f32,
+    hz: f32,
+    beats: f64,
+    tempo: f64,
+    synced: bool,
+    state: [Channel; 2],
+    /// High-pass and low-pass of the low cut's crossover; None when off.
+    low_cut: Option<(SvfCoef, SvfCoef)>,
+    fade_step: f32,
+    smooth: f32,
+    depth: f32,
+    output: f32,
+    bypass: f32,
+    fresh: bool,
+}
+
+impl Engine {
+    pub fn new(rate: f32, channels: usize) -> Result<Self, &'static str> {
+        if !(8000.0..=768000.).contains(&rate) {
+            return Err("unsupported sample rate");
+        }
+        if !(1..=2).contains(&channels) {
+            return Err("unsupported channel count");
+        }
+        let tracker = Tracker::new(rate, TrackerConfig::BASS);
+        let latency = tracker.latency();
+        // The copy reads up to half a period (plus a fade) on either side of the dry path.
+        let reach = (rate / MIN_HZ).ceil() as usize + 8;
+        let mut e = Self {
+            rate,
+            channels,
+            settings: Settings::default(),
+            latency,
+            audio: vec![[0.; 2]; latency + reach],
+            audio_at: 0,
+            tracker,
+            pitch: PitchFollower::default(),
+            pitch_coef: coefficient(rate, PITCH_MS),
+            hz: 0.,
+            beats: 0.,
+            tempo: DEFAULT_TEMPO,
+            synced: false,
+            state: [Channel::default(); 2],
+            low_cut: None,
+            fade_step: 1. / (rate * FADE_MS * 0.001),
+            smooth: coefficient(rate, 10.),
+            depth: 0.,
+            output: 1.,
+            bypass: 0.,
+            fresh: true,
+        };
+        e.set_settings(Settings::default())?;
+        e.fresh = true;
+        Ok(e)
+    }
+    pub fn latency_samples(&self) -> u32 {
+        self.latency as u32
+    }
+    pub fn channels(&self) -> usize {
+        self.channels
+    }
+    pub fn settings(&self) -> Settings {
+        self.settings
+    }
+    pub fn set_settings(&mut self, s: Settings) -> Result<(), &'static str> {
+        s.validate()?;
+        // Unsure tracking sends no events, so the beating holds its last sure note.
+        self.tracker
+            .set(s.pitch.source(s.source.mode(), s.gate, true));
+        if s.low_cut != self.settings.low_cut || self.fresh {
+            let q = std::f32::consts::FRAC_1_SQRT_2;
+            let hz = s.low_cut.min(0.45 * self.rate);
+            self.low_cut = (s.low_cut >= LOW_CUT_OFF).then(|| {
+                (
+                    SvfCoef::highpass(self.rate, hz, q),
+                    SvfCoef::lowpass(self.rate, hz, q),
+                )
+            });
+        }
+        self.settings = s;
+        if std::mem::take(&mut self.fresh) {
+            self.depth = s.depth * 0.01;
+            self.output = db_to_gain(s.output);
+            self.bypass = f32::from(s.bypass);
+        }
+        Ok(())
+    }
+    /// Tempo and, while the host plays, its beat position in quarter notes at the first
+    /// input sample of the next block. Without a position the beat runs on freely.
+    pub fn set_transport(&mut self, tempo: Option<f64>, position: Option<f64>) {
+        self.tempo = tempo
+            .filter(|t| t.is_finite() && *t > 0.)
+            .unwrap_or(DEFAULT_TEMPO)
+            .clamp(20., 999.);
+        match position.filter(|p| p.is_finite()) {
+            Some(p) => {
+                // The output lags the input by the lookahead, and the host compensates it:
+                // what leaves now belongs `latency` samples earlier on the timeline.
+                self.beats = p - self.latency as f64 / self.rate as f64 * self.tempo / 60.;
+                self.synced = true;
+            }
+            None => self.synced = false,
+        }
+    }
+    pub fn reset(&mut self) {
+        self.audio.fill([0.; 2]);
+        self.tracker.reset();
+        self.pitch = PitchFollower::default();
+        self.hz = 0.;
+        self.state = [Channel::default(); 2];
+        self.fresh = true;
+    }
+    pub fn note_on(&mut self, note: u8) {
+        self.tracker.note_on(note);
+    }
+    pub fn note_off(&mut self, note: u8) {
+        self.tracker.note_off(note);
+    }
+    /// The audio `back` samples (fractional) before the newest one, cubic Hermite.
+    #[inline]
+    fn read(&self, back: f32, c: usize) -> f32 {
+        let len = self.audio.len();
+        let back = back.clamp(1., (len - 3) as f32);
+        let whole = back.floor();
+        let t = back - whole;
+        let base = whole as usize;
+        let at = |back: usize| self.audio[(self.audio_at + len - back) % len][c];
+        // y0 is one sample newer than y1; y2 and y3 are older.
+        let (y0, y1, y2, y3) = (at(base - 1), at(base), at(base + 1), at(base + 2));
+        let c1 = 0.5 * (y2 - y0);
+        let c2 = y0 - 2.5 * y1 + 2. * y2 - 0.5 * y3;
+        let c3 = 0.5 * (y3 - y0) + 1.5 * (y1 - y2);
+        ((c3 * t + c2) * t + c1) * t + y1
+    }
+    // Channels index the input, the state and the output at once.
+    #[allow(clippy::needless_range_loop)]
+    pub fn process_sample(&mut self, x: [f32; 2]) -> [f32; 2] {
+        let mono = if self.channels == 2 {
+            0.5 * (x[0] + x[1])
+        } else {
+            x[0]
+        };
+        let (pitch, snap) = (&mut self.pitch, self.settings.snap);
+        self.tracker.process(mono, |e| pitch.event(snap, e));
+        let (hz, jump) = self.pitch.step(self.pitch_coef);
+        self.hz = hz;
+        let len = self.audio.len();
+        self.audio_at = (self.audio_at + 1) % len;
+        self.audio[self.audio_at] = x;
+
+        let s = self.settings;
+        approach(&mut self.depth, s.depth * 0.01, self.smooth);
+        approach(&mut self.output, db_to_gain(s.output), self.smooth);
+        approach(&mut self.bypass, f32::from(s.bypass), self.smooth);
+
+        let period = self.rate / if hz > 0. { hz } else { FALLBACK_HZ };
+        let step = self.tempo / 60. / self.rate as f64 / s.rate.quarters() / s.harmonic as f64;
+        let centre = self.latency as f32;
+        let mut out = [0.; 2];
+        for c in 0..self.channels {
+            // Position in beat cycles of the chosen harmonic, shifted so a cycle starts at
+            // the delay's highest point and the beat peaks (delay = centre) at cycle 0.
+            let u = cycles(&s, self.beats, c) / s.harmonic as f64 + 0.5;
+            let ch = self.state[c];
+            let moved = (u - ch.last - step).abs() > JUMP;
+            let mut ch = ch;
+            if !ch.started || jump || moved || u.floor() != ch.whole {
+                if ch.started {
+                    ch.old = ch.active;
+                    ch.fade = 1.;
+                }
+                ch.whole = u.floor();
+                ch.started = true;
+            }
+            let delay = centre + period * (0.5 - (u - ch.whole) as f32);
+            ch.active.slope = if ch.fade == 1. {
+                0.
+            } else {
+                delay - ch.active.delay
+            };
+            ch.active.delay = delay;
+            ch.last = u;
+            let mut copy = self.read(ch.active.delay, c);
+            if ch.fade > 0. {
+                ch.old.delay += ch.old.slope;
+                let w = ch.fade * ch.fade * (3. - 2. * ch.fade);
+                copy += (self.read(ch.old.delay, c) - copy) * w;
+                ch.fade = (ch.fade - self.fade_step).max(0.);
+            }
+            let delayed = self.audio[(self.audio_at + len - self.latency) % len][c];
+            let g = self.depth;
+            let norm = 1. / (1. + g * g).sqrt();
+            let wet = match &self.low_cut {
+                Some((high, low)) => {
+                    let lr4 = |f: &mut [Svf; 2], c: &SvfCoef, x: f32| {
+                        let first = f[0].process(c, x);
+                        f[1].process(c, first)
+                    };
+                    let copy = lr4(&mut ch.copy_high, high, copy);
+                    let above = lr4(&mut ch.high, high, delayed);
+                    let below = lr4(&mut ch.low, low, delayed);
+                    below + (above + g * copy) * norm
+                }
+                None => (delayed + g * copy) * norm,
+            };
+            self.state[c] = ch;
+            out[c] = wet * self.output * (1. - self.bypass) + delayed * self.bypass;
+        }
+        self.beats += self.tempo / 60. / self.rate as f64;
+        out
+    }
+    pub fn take_analyzer(&self) -> AnalyzerFrame {
+        let s = self.settings;
+        let hz = self.hz;
+        let mut f = AnalyzerFrame {
+            hz,
+            beats: self.beats,
+            tempo: self.tempo,
+            synced: self.synced,
+            latency: self.latency as u32,
+            sample_rate: self.rate,
+            ..AnalyzerFrame::default()
+        };
+        if hz > 0. {
+            let beat_hz = self.tempo / 60. / s.rate.quarters();
+            f.ratio = 1. + (beat_hz / (s.harmonic as f64 * hz as f64)) as f32;
+        }
+        if self.tracker.active() && hz > 0. {
+            f.note = Some(hz_to_midi(hz).round().clamp(0., 127.) as u8);
+        }
+        f
+    }
+}
+
+/// One-pole step that lands exactly on the target, so switched states end bit-exact.
+fn approach(value: &mut f32, target: f32, coef: f32) {
+    *value += (target - *value) * coef;
+    if (target - *value).abs() < 1e-6 {
+        *value = target;
+    }
+}
@@ -0,0 +1,170 @@
+//! Host-independent controls. Levels in dB, amounts in percent, angles in degrees.
+use common_dsp::tracker::{Pitch, PitchMode};
+use serde::{Deserialize, Serialize};
+
+/// Highest harmonic the beat rate can be set on.
+pub const HARMONIC_MAX: u32 = 8;
+pub const LOW_CUT_MAX: f32 = 400.;
+/// A low cut below this is off: no filter on either path.
+pub const LOW_CUT_OFF: f32 = 20.;
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
+pub enum Source {
+    /// Pitch and note starts are detected from the incoming bass.
+    #[default]
+    Audio,
+    /// Notes come from MIDI note input.
+    Midi,
+    /// Note starts are detected, the pitch is the set note: nothing is guessed.
+    Note,
+}
+impl Source {
+    pub fn mode(self) -> PitchMode {
+        match self {
+            Source::Audio => PitchMode::Audio,
+            Source::Midi => PitchMode::Midi,
+            Source::Note => PitchMode::Note,
+        }
+    }
+    pub fn from_mode(mode: PitchMode) -> Self {
+        match mode {
+            PitchMode::Audio => Source::Audio,
+            PitchMode::Midi => Source::Midi,
+            PitchMode::Note => Source::Note,
+        }
+    }
+}
+
+/// One beat cycle lasts this note value.
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
+pub enum Rate {
+    Whole,
+    Half,
+    Quarter,
+    #[default]
+    Eighth,
+    Sixteenth,
+    ThirtySecond,
+    QuarterTriplet,
+    EighthTriplet,
+    SixteenthTriplet,
+}
+impl Rate {
+    pub const ALL: [Rate; 9] = [
+        Rate::Whole,
+        Rate::Half,
+        Rate::Quarter,
+        Rate::Eighth,
+        Rate::Sixteenth,
+        Rate::ThirtySecond,
+        Rate::QuarterTriplet,
+        Rate::EighthTriplet,
+        Rate::SixteenthTriplet,
+    ];
+    /// Length of one beat cycle in quarter notes.
+    pub fn quarters(self) -> f64 {
+        match self {
+            Rate::Whole => 4.,
+            Rate::Half => 2.,
+            Rate::Quarter => 1.,
+            Rate::Eighth => 0.5,
+            Rate::Sixteenth => 0.25,
+            Rate::ThirtySecond => 0.125,
+            Rate::QuarterTriplet => 2. / 3.,
+            Rate::EighthTriplet => 1. / 3.,
+            Rate::SixteenthTriplet => 1. / 6.,
+        }
+    }
+    pub fn label(self) -> &'static str {
+        match self {
+            Rate::Whole => "1/1",
+            Rate::Half => "1/2",
+            Rate::Quarter => "1/4",
+            Rate::Eighth => "1/8",
+            Rate::Sixteenth => "1/16",
+            Rate::ThirtySecond => "1/32",
+            Rate::QuarterTriplet => "1/4T",
+            Rate::EighthTriplet => "1/8T",
+            Rate::SixteenthTriplet => "1/16T",
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq)]
+#[serde(deny_unknown_fields)]
+pub struct Settings {
+    pub source: Source,
+    /// Note mode's note, the key lock and Follow bends.
+    #[serde(default)]
+    pub pitch: Pitch,
+    /// How long one beat cycle of `harmonic` lasts.
+    pub rate: Rate,
+    /// The harmonic that beats exactly at `rate`. Harmonic n beats n/harmonic times as fast.
+    pub harmonic: u32,
+    /// Level of the detuned copy against the bass. 100 % gives full nulls.
+    pub depth: f32,
+    /// Below this frequency the copy is removed, so the sub stays steady and mono-safe.
+    /// Under `LOW_CUT_OFF` Hz the filter is off.
+    pub low_cut: f32,
+    /// Moves the right channel's beat against the left, up to half a cycle.
+    pub width: f32,
+    /// Where in the cycle the beat peaks, in degrees. 0 puts the peak on the beat.
+    pub phase: f32,
+    /// Detection threshold in dBFS for note starts (Audio source).
+    pub gate: f32,
+    /// Round detected pitch to the nearest semitone. Off by default: the copy jumps by one
+    /// period of the pitch in use, and a period that does not fit the note is heard.
+    pub snap: bool,
+    pub output: f32,
+    pub bypass: bool,
+}
+impl Default for Settings {
+    fn default() -> Self {
+        Self {
+            source: Source::Audio,
+            pitch: Pitch::default(),
+            rate: Rate::Eighth,
+            // Harmonic 4 sits above the low cut on every bass note, and on F1 it asks for
+            // about 45 cents of detune, a usual reese spread.
+            harmonic: 4,
+            depth: 70.,
+            low_cut: 100.,
+            width: 0.,
+            phase: 0.,
+            gate: -48.,
+            snap: false,
+            output: 0.,
+            bypass: false,
+        }
+    }
+}
+impl Settings {
+    pub fn validate(&self) -> Result<(), &'static str> {
+        self.pitch.validate()?;
+        let finite = [
+            self.depth,
+            self.low_cut,
+            self.width,
+            self.phase,
+            self.gate,
+            self.output,
+        ]
+        .iter()
+        .all(|v| v.is_finite());
+        if !finite {
+            return Err("non-finite setting");
+        }
+        let ok = (1..=HARMONIC_MAX).contains(&self.harmonic)
+            && (0.0..=100.).contains(&self.depth)
+            && (0.0..=LOW_CUT_MAX).contains(&self.low_cut)
+            && (0.0..=100.).contains(&self.width)
+            && (0.0..=360.).contains(&self.phase)
+            && (-60.0..=-20.).contains(&self.gate)
+            && (-12.0..=12.).contains(&self.output);
+        if ok {
+            Ok(())
+        } else {
+            Err("setting out of range")
+        }
+    }
+}
@@ -0,0 +1,278 @@
+// Sample indices address several signals at once.
+#![allow(clippy::needless_range_loop)]
+use braze_core::{cycles, envelope, Engine, Rate, Settings};
+use common_dsp::Saw;
+use std::f32::consts::TAU;
+
+const RATE: f32 = 48000.;
+const TEMPO: f64 = 120.;
+
+fn engine(s: Settings) -> (Engine, usize) {
+    let mut e = Engine::new(RATE, 2).unwrap();
+    e.set_settings(s).unwrap();
+    e.set_transport(Some(TEMPO), Some(0.));
+    let l = e.latency_samples() as usize;
+    (e, l)
+}
+fn seconds(t: f32) -> usize {
+    (t * RATE) as usize
+}
+fn render(e: &mut Engine, x: &[f32]) -> Vec<[f32; 2]> {
+    x.iter().map(|&s| e.process_sample([s, s])).collect()
+}
+/// A saw at `hz` from 0.05 s on, with a 1 ms fade-in.
+fn saw(hz: f32, total: f32) -> Vec<f32> {
+    let mut osc = Saw::new(RATE, hz);
+    (0..seconds(total))
+        .map(|i| {
+            let start = seconds(0.05);
+            if i < start {
+                return 0.;
+            }
+            0.5 * osc.sample() * ((i - start) as f32 / seconds(0.001) as f32).min(1.)
+        })
+        .collect()
+}
+/// Amplitude of harmonic `n` of `hz` over one period centred on sample `at`.
+fn harmonic(x: &[f32], at: usize, hz: f32, n: u32) -> f32 {
+    let half = (RATE / hz / 2.).round() as usize;
+    let w = TAU * hz * n as f32 / RATE;
+    let (mut re, mut im) = (0f32, 0f32);
+    for i in at - half..at + half {
+        re += x[i] * (w * i as f32).cos();
+        im -= x[i] * (w * i as f32).sin();
+    }
+    2. * (re * re + im * im).sqrt() / (2 * half) as f32
+}
+/// Beat position (quarter notes) of output sample `i`.
+fn beats(i: usize, latency: usize) -> f64 {
+    (i as f64 - latency as f64) / RATE as f64 * TEMPO / 60.
+}
+
+/// Harmonics 1–4 of A1 at falling levels, a periodic note the tracker reads exactly.
+fn partials(t: f64) -> f64 {
+    (1..=4)
+        .map(|n| 0.4 / n as f64 * (std::f64::consts::TAU * 55. * n as f64 * t).sin())
+        .sum()
+}
+
+#[test]
+fn every_harmonic_beats_on_the_tempo_grid() {
+    for (harmonic, rate) in [(1, Rate::Eighth), (2, Rate::Sixteenth), (3, Rate::Quarter)] {
+        let s = Settings {
+            harmonic,
+            rate,
+            depth: 100.,
+            snap: true,
+            low_cut: 0.,
+            ..Settings::default()
+        };
+        let (mut e, l) = engine(s);
+        let x: Vec<f32> = (0..seconds(1.5))
+            .map(|i| partials(i as f64 / RATE as f64) as f32)
+            .collect();
+        let y = render(&mut e, &x);
+        let mut worst = 0f32;
+        for i in seconds(0.5)..seconds(1.4) {
+            // Cycles of the chosen harmonic, from the grid alone: peaks on every multiple
+            // of `rate`. The copy lags the bass by (0.5 − frac(u)) periods.
+            let u = beats(i, l) / rate.quarters() / harmonic as f64 + 0.5;
+            let t = (i - l) as f64 / RATE as f64;
+            let lag = (0.5 - u.fract()) / 55.;
+            let ideal = (partials(t) + partials(t - lag)) / 2f64.sqrt();
+            worst = worst.max((y[i][0] - ideal as f32).abs());
+        }
+        assert!(worst < 3e-3, "harmonic {harmonic}, {rate:?}: {worst}");
+    }
+}
+
+#[test]
+fn envelope_peaks_on_the_grid_and_harmonic_n_beats_n_over_k_as_fast() {
+    let s = Settings {
+        harmonic: 2,
+        ..Settings::default()
+    };
+    // At cycle 0 every harmonic peaks: twice the bass, less the loudness correction.
+    for n in 1..=8 {
+        assert!((envelope(&s, n, 0., 1.) - 2f32.sqrt()).abs() < 1e-5);
+    }
+    // Harmonic 2 nulls half a cycle later; harmonic 1, beating half as fast, a cycle later.
+    assert!(envelope(&s, 2, 0.5, 1.) < 1e-5);
+    assert!(envelope(&s, 1, 1., 1.) < 1e-5);
+    assert!(envelope(&s, 4, 0.25, 1.) < 1e-5);
+}
+
+#[test]
+fn the_copy_is_seamless_across_its_jumps() {
+    // A pure sine at exactly A1: the ideal copy is a smooth sine whose phase follows the beat.
+    let s = Settings {
+        harmonic: 1,
+        rate: Rate::Sixteenth,
+        depth: 100.,
+        snap: true,
+        low_cut: 0.,
+        ..Settings::default()
+    };
+    let (mut e, l) = engine(s);
+    let x: Vec<f32> = (0..seconds(1.5))
+        .map(|i| 0.5 * (TAU * 55. * i as f32 / RATE).sin())
+        .collect();
+    let y = render(&mut e, &x);
+    let mut worst = 0f32;
+    for i in seconds(0.5)..seconds(1.4) {
+        let u = cycles(&s, beats(i, l), 0) + 0.5;
+        let dry = x[i - l];
+        let phase = TAU as f64 * (55. * (i - l) as f64 / RATE as f64 + u.fract());
+        let copy = -0.5 * phase.sin() as f32;
+        let ideal = (dry + copy) / 2f32.sqrt();
+        worst = worst.max((y[i][0] - ideal).abs());
+    }
+    assert!(worst < 2e-3, "{worst}");
+}
+
+#[test]
+fn depth_zero_is_the_delayed_input() {
+    let (mut e, l) = engine(Settings {
+        depth: 0.,
+        low_cut: 0.,
+        ..Settings::default()
+    });
+    let x = saw(55., 0.6);
+    let y = render(&mut e, &x);
+    for i in l..x.len() {
+        assert_eq!(y[i][0], x[i - l]);
+    }
+}
+
+#[test]
+fn width_moves_the_right_channel_half_a_cycle() {
+    let s = Settings {
+        harmonic: 1,
+        width: 100.,
+        depth: 100.,
+        rate: Rate::Quarter,
+        low_cut: 0.,
+        ..Settings::default()
+    };
+    let (mut e, l) = engine(s);
+    let x = saw(55., 1.5);
+    let y = render(&mut e, &x);
+    let left: Vec<f32> = y.iter().map(|v| v[0]).collect();
+    let right: Vec<f32> = y.iter().map(|v| v[1]).collect();
+    // On the beat the left fundamental peaks and the right one nulls; half a beat later
+    // they swap.
+    for (beat, loud, quiet) in [
+        (1., &left, &right),
+        (1.5, &right, &left),
+        (2., &left, &right),
+    ] {
+        let at = l + (beat / (TEMPO / 60.) * RATE as f64) as usize;
+        let (a, b) = (harmonic(loud, at, 55., 1), harmonic(quiet, at, 55., 1));
+        assert!(20. * (a / b).log10() > 20., "beat {beat}: {a} vs {b}");
+    }
+}
+
+#[test]
+fn note_changes_and_transport_jumps_do_not_click() {
+    let s = Settings {
+        depth: 100.,
+        ..Settings::default()
+    };
+    let (mut e, _) = engine(s);
+    // Phase-continuous sine from A1 to D2, no gap.
+    let mut phase = 0f32;
+    let x: Vec<f32> = (0..seconds(1.2))
+        .map(|i| {
+            let hz = if i < seconds(0.6) { 55. } else { 73.42 };
+            phase = (phase + hz / RATE).fract();
+            0.5 * (TAU * phase).sin()
+        })
+        .collect();
+    let mut y = Vec::new();
+    for (i, &v) in x.iter().enumerate() {
+        if i == seconds(0.9) {
+            // A locate to another bar.
+            e.set_transport(Some(TEMPO), Some(37.3));
+        }
+        y.push(e.process_sample([v, v])[0]);
+    }
+    // Two sines of peak 0.5 at up to 79 Hz move at most this much per sample (after the
+    // loudness correction), plus some room for the fades.
+    let bound = 2. * 0.5 * TAU * 79. / RATE / 2f32.sqrt() * 1.5;
+    for i in seconds(0.2)..y.len() - 1 {
+        assert!(
+            (y[i + 1] - y[i]).abs() < bound,
+            "{i}: {}",
+            (y[i + 1] - y[i]).abs()
+        );
+    }
+}
+
+#[test]
+fn low_cut_keeps_the_sub_steady_and_the_beat_on_the_grid() {
+    let s = Settings {
+        harmonic: 1,
+        depth: 100.,
+        rate: Rate::Half,
+        low_cut: 150.,
+        ..Settings::default()
+    };
+    let (mut e, l) = engine(s);
+    let x = saw(55., 2.4);
+    let y: Vec<f32> = render(&mut e, &x).iter().map(|v| v[0]).collect();
+    // One cycle (a half note, 1 s at 120 BPM): the fundamental, under the cut, does not beat.
+    let sub: Vec<f32> = (0..50)
+        .map(|k| harmonic(&y, seconds(1.) + k * seconds(0.02), 55., 1))
+        .collect();
+    let (lo, hi) = sub
+        .iter()
+        .fold((f32::MAX, 0f32), |(a, b), &v| (a.min(v), b.max(v)));
+    // Without the cut it would null fully; what remains is leakage of the beating
+    // harmonics into the one-period window.
+    assert!(20. * (hi / lo).log10() < 1.5, "{lo} .. {hi}");
+    // And it keeps its level: the loudness correction for the copy applies above the cut.
+    let dry = harmonic(&x, seconds(1.) - l, 55., 1);
+    let mean = sub.iter().sum::<f32>() / sub.len() as f32;
+    assert!((20. * (mean / dry).log10()).abs() < 0.5, "{mean} vs {dry}");
+    // Harmonic 6 (330 Hz) beats 6 times per cycle: it peaks on the grid, the high-pass's
+    // phase is matched on the bass, and nulls 1/12 cycle later.
+    for beat in [2., 4.] {
+        let peak = l + (beat / (TEMPO / 60.) * RATE as f64) as usize;
+        let null = peak + (RATE / 12.) as usize;
+        let (a, b) = (harmonic(&y, peak, 55., 6), harmonic(&y, null, 55., 6));
+        assert!(20. * (a / b).log10() > 15., "beat {beat}: {a} vs {b}");
+    }
+}
+
+#[test]
+fn the_ratio_follows_the_note() {
+    let (mut e, _) = engine(Settings {
+        harmonic: 1,
+        ..Settings::default()
+    });
+    for hz in [55., 110.] {
+        let x = saw(hz, 0.5);
+        render(&mut e, &x);
+        let f = e.take_analyzer();
+        // An eighth at 120 BPM beats 4 times per second: r = 1 + 4 / f0.
+        assert!((f.ratio - (1. + 4. / hz)).abs() < 2e-3, "{hz}: {}", f.ratio);
+    }
+}
+
+#[test]
+fn settings_are_validated_and_serialise() {
+    let mut e = Engine::new(RATE, 1).unwrap();
+    assert!(e
+        .set_settings(Settings {
+            harmonic: 0,
+            ..Settings::default()
+        })
+        .is_err());
+    let json = serde_json::to_string(&Settings::default()).unwrap();
+    assert_eq!(
+        serde_json::from_str::<Settings>(&json).unwrap(),
+        Settings::default()
+    );
+    assert!(Engine::new(1000., 2).is_err());
+    assert!(Engine::new(48000., 3).is_err());
+}
@@ -0,0 +1,79 @@
+use braze_core::{Engine, Rate, Settings, Source};
+use std::{
+    alloc::{GlobalAlloc, Layout, System},
+    cell::Cell,
+};
+
+struct CheckedAllocator;
+thread_local! {
+    static CHECK:Cell<bool>=const {Cell::new(false)};
+    static OPERATIONS:Cell<usize>=const {Cell::new(0)};
+}
+fn record() {
+    if CHECK.try_with(Cell::get).unwrap_or(false) {
+        let _ = OPERATIONS.try_with(|n| n.set(n.get() + 1));
+    }
+}
+unsafe impl GlobalAlloc for CheckedAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        record();
+        unsafe { System.alloc(layout) }
+    }
+    unsafe fn dealloc(&self, pointer: *mut u8, layout: Layout) {
+        record();
+        unsafe { System.dealloc(pointer, layout) }
+    }
+    unsafe fn realloc(&self, pointer: *mut u8, layout: Layout, size: usize) -> *mut u8 {
+        record();
+        unsafe { System.realloc(pointer, layout, size) }
+    }
+}
+#[global_allocator]
+static ALLOCATOR: CheckedAllocator = CheckedAllocator;
+
+#[test]
+fn processing_notes_settings_transport_and_analysis_do_not_allocate_or_free() {
+    let mut engine = Engine::new(48000., 2).unwrap();
+    let mut settings = Settings {
+        width: 50.,
+        ..Settings::default()
+    };
+    engine.set_settings(settings).unwrap();
+    CHECK.with(|v| v.set(true));
+    for i in 0..96000 {
+        if i % 512 == 0 {
+            let playing = (i / 24000) % 2 == 0;
+            engine.set_transport(
+                Some(140.),
+                playing.then_some(i as f64 / 48000. * 140. / 60.),
+            );
+        }
+        if i % 4800 == 0 {
+            settings.rate = Rate::ALL[(i / 4800) % Rate::ALL.len()];
+            settings.harmonic = 1 + (i / 4800 % 4) as u32;
+            settings.source = if i > 48000 {
+                Source::Midi
+            } else {
+                Source::Audio
+            };
+            engine.set_settings(settings).unwrap();
+            engine.note_on(30 + (i / 4800 % 12) as u8);
+        }
+        if i % 4800 == 2400 {
+            engine.note_off(30 + (i / 4800 % 12) as u8);
+        }
+        let t = i as f32 / 48000.;
+        let x = if (i / 2400) % 2 == 0 {
+            (std::f32::consts::TAU * 55. * t).sin() * 0.5
+        } else {
+            0.
+        };
+        std::hint::black_box(engine.process_sample([x, x]));
+        if i % 1600 == 0 {
+            std::hint::black_box(engine.take_analyzer());
+        }
+    }
+    engine.reset();
+    CHECK.with(|v| v.set(false));
+    assert_eq!(OPERATIONS.with(Cell::get), 0);
+}
@@ -0,0 +1,26 @@
+[package]
+name = "braze"
+version = "0.2.0"
+edition = "2021"
+license = "ISC"
+
+[workspace]
+
+[lib]
+crate-type = ["cdylib", "rlib"]
+
+[dependencies]
+nih_plug = { git = "https://github.com/robbert-vdh/nih-plug.git", rev = "de421011f41a6d10fc8c7a6084e4f4dee0143683", default-features = false }
+nih_plug_egui = { git = "https://github.com/robbert-vdh/nih-plug.git", rev = "de421011f41a6d10fc8c7a6084e4f4dee0143683" }
+braze-core = { path = "../core" }
+common-params = { path = "../../common/params" }
+braze-ui = { path = "../ui" }
+crossbeam-queue = "0.3"
+
+[dev-dependencies]
+clap-sys = { git = "https://github.com/micahrj/clap-sys.git", rev = "25d7f53fdb6363ad63fbd80049cb7a42a97ac156" }
+serde_json = "1"
+
+[profile.release]
+lto = "thin"
+strip = "symbols"
@@ -0,0 +1,193 @@
+//! CLAP audio effect. All DSP state is owned by the processing thread.
+mod params;
+use braze_core::{AnalyzerFrame, Engine};
+use crossbeam_queue::ArrayQueue;
+use nih_plug::prelude::*;
+use nih_plug_egui::{create_egui_editor, egui};
+use params::{BrazeParams, FLOATS};
+use std::sync::Arc;
+
+struct EditorData {
+    ui: braze_ui::State,
+    gestures: [bool; FLOATS],
+}
+pub struct Braze {
+    params: Arc<BrazeParams>,
+    analyzer: Arc<ArrayQueue<AnalyzerFrame>>,
+    engine: Option<Engine>,
+    publish_count: usize,
+    publish_interval: usize,
+}
+impl Default for Braze {
+    fn default() -> Self {
+        Self {
+            params: Arc::new(BrazeParams::default()),
+            analyzer: Arc::new(ArrayQueue::new(2)),
+            engine: None,
+            publish_count: 0,
+            publish_interval: 1600,
+        }
+    }
+}
+impl Plugin for Braze {
+    const NAME: &'static str = "Braze";
+    const VENDOR: &'static str = "Bass Foundry";
+    const URL: &'static str = "";
+    const EMAIL: &'static str = "";
+    const VERSION: &'static str = env!("CARGO_PKG_VERSION");
+    const AUDIO_IO_LAYOUTS: &'static [AudioIOLayout] = &[
+        AudioIOLayout {
+            main_input_channels: NonZeroU32::new(2),
+            main_output_channels: NonZeroU32::new(2),
+            ..AudioIOLayout::const_default()
+        },
+        AudioIOLayout {
+            main_input_channels: NonZeroU32::new(1),
+            main_output_channels: NonZeroU32::new(1),
+            ..AudioIOLayout::const_default()
+        },
+    ];
+    const MIDI_INPUT: MidiConfig = MidiConfig::Basic;
+    const SAMPLE_ACCURATE_AUTOMATION: bool = false;
+    type SysExMessage = ();
+    type BackgroundTask = ();
+    fn params(&self) -> Arc<dyn Params> {
+        self.params.clone()
+    }
+    fn editor(&mut self, _: AsyncExecutor<Self>) -> Option<Box<dyn Editor>> {
+        let params = self.params.clone();
+        let analyzer = self.analyzer.clone();
+        create_egui_editor(
+            params.editor.clone(),
+            EditorData {
+                ui: braze_ui::State::default(),
+                gestures: [false; FLOATS],
+            },
+            |ctx, _| braze_ui::style(ctx),
+            move |ctx, setter, data| {
+                while let Some(frame) = analyzer.pop() {
+                    data.ui.accept_frame(frame);
+                }
+                let before = params.settings();
+                let mut edited = before;
+                nih_plug_egui::resizable_window::ResizableWindow::new("braze-editor")
+                    .min_size(egui::vec2(
+                        braze_ui::WIDTH as f32 - 80.,
+                        braze_ui::HEIGHT as f32 - 40.,
+                    ))
+                    .show(ctx, &params.editor, |ui| {
+                        braze_ui::show(ui, &mut edited, &mut data.ui)
+                    });
+                params.apply(
+                    setter,
+                    &before,
+                    &edited,
+                    data.ui.gesture_active,
+                    &mut data.gestures,
+                );
+                // The playhead follows the transport.
+                ctx.request_repaint_after(std::time::Duration::from_millis(40));
+            },
+        )
+    }
+    fn initialize(
+        &mut self,
+        layout: &AudioIOLayout,
+        config: &BufferConfig,
+        context: &mut impl InitContext<Self>,
+    ) -> bool {
+        let Ok(mut engine) = Engine::new(
+            config.sample_rate,
+            layout.main_input_channels.map_or(0, |v| v.get() as usize),
+        ) else {
+            return false;
+        };
+        let settings = self.params.settings();
+        if engine.set_settings(settings).is_err() {
+            return false;
+        }
+        context.set_latency_samples(engine.latency_samples());
+        self.publish_interval = (config.sample_rate / 30.) as usize;
+        self.engine = Some(engine);
+        true
+    }
+    fn reset(&mut self) {
+        if let Some(e) = self.engine.as_mut() {
+            e.reset();
+        }
+        self.publish_count = 0;
+    }
+    fn process(
+        &mut self,
+        buffer: &mut Buffer,
+        _: &mut AuxiliaryBuffers,
+        context: &mut impl ProcessContext<Self>,
+    ) -> ProcessStatus {
+        let Some(engine) = self.engine.as_mut() else {
+            return ProcessStatus::Normal;
+        };
+        let settings = self.params.settings();
+        let _ = engine.set_settings(settings);
+        let transport = context.transport();
+        engine.set_transport(
+            transport.tempo,
+            if transport.playing {
+                transport.pos_beats()
+            } else {
+                None
+            },
+        );
+        let mut next = context.next_event();
+        for (index, mut sample) in buffer.iter_samples().enumerate() {
+            while let Some(event) = next {
+                if event.timing() as usize > index {
+                    break;
+                }
+                match event {
+                    NoteEvent::NoteOn { note, velocity, .. } if velocity > 0. => {
+                        engine.note_on(note)
+                    }
+                    NoteEvent::NoteOn { note, .. } | NoteEvent::NoteOff { note, .. } => {
+                        engine.note_off(note)
+                    }
+                    NoteEvent::Choke { note, .. } => engine.note_off(note),
+                    _ => {}
+                }
+                next = context.next_event();
+            }
+            let x = [
+                *sample.get_mut(0).unwrap(),
+                if engine.channels() == 2 {
+                    *sample.get_mut(1).unwrap()
+                } else {
+                    0.
+                },
+            ];
+            let out = engine.process_sample(x);
+            for (c, value) in sample.into_iter().enumerate() {
+                *value = out[c];
+            }
+            self.publish_count += 1;
+            if self.publish_count >= self.publish_interval {
+                self.analyzer.force_push(engine.take_analyzer());
+                self.publish_count = 0;
+            }
+        }
+        // The lookahead delay must drain after input stops.
+        ProcessStatus::KeepAlive
+    }
+}
+impl ClapPlugin for Braze {
+    const CLAP_ID: &'static str = "io.narl.bass-foundry.braze";
+    const CLAP_DESCRIPTION: Option<&'static str> =
+        Some("Adds a detuned copy whose beating stays on the tempo grid on every note");
+    const CLAP_MANUAL_URL: Option<&'static str> = None;
+    const CLAP_SUPPORT_URL: Option<&'static str> = None;
+    const CLAP_FEATURES: &'static [ClapFeature] = &[
+        ClapFeature::AudioEffect,
+        ClapFeature::Chorus,
+        ClapFeature::Stereo,
+        ClapFeature::Mono,
+    ];
+}
+nih_export_clap!(Braze);
@@ -0,0 +1,238 @@
+use braze_core::{Rate, Settings, Source, HARMONIC_MAX, LOW_CUT_MAX};
+use common_params::PitchParams;
+use nih_plug::prelude::*;
+use nih_plug_egui::EguiState;
+use std::sync::Arc;
+
+#[derive(Enum, Debug, PartialEq, Eq, Clone, Copy)]
+pub enum SourceParam {
+    #[id = "audio"]
+    Audio,
+    #[id = "midi"]
+    #[name = "MIDI"]
+    Midi,
+    #[id = "note"]
+    Note,
+}
+impl From<SourceParam> for Source {
+    fn from(s: SourceParam) -> Self {
+        match s {
+            SourceParam::Audio => Source::Audio,
+            SourceParam::Midi => Source::Midi,
+            SourceParam::Note => Source::Note,
+        }
+    }
+}
+impl From<Source> for SourceParam {
+    fn from(s: Source) -> Self {
+        match s {
+            Source::Audio => SourceParam::Audio,
+            Source::Midi => SourceParam::Midi,
+            Source::Note => SourceParam::Note,
+        }
+    }
+}
+#[derive(Enum, Debug, PartialEq, Eq, Clone, Copy)]
+pub enum RateParam {
+    #[id = "1-1"]
+    #[name = "1/1"]
+    Whole,
+    #[id = "1-2"]
+    #[name = "1/2"]
+    Half,
+    #[id = "1-4"]
+    #[name = "1/4"]
+    Quarter,
+    #[id = "1-8"]
+    #[name = "1/8"]
+    Eighth,
+    #[id = "1-16"]
+    #[name = "1/16"]
+    Sixteenth,
+    #[id = "1-32"]
+    #[name = "1/32"]
+    ThirtySecond,
+    #[id = "1-4t"]
+    #[name = "1/4T"]
+    QuarterTriplet,
+    #[id = "1-8t"]
+    #[name = "1/8T"]
+    EighthTriplet,
+    #[id = "1-16t"]
+    #[name = "1/16T"]
+    SixteenthTriplet,
+}
+const RATES: [(RateParam, Rate); 9] = [
+    (RateParam::Whole, Rate::Whole),
+    (RateParam::Half, Rate::Half),
+    (RateParam::Quarter, Rate::Quarter),
+    (RateParam::Eighth, Rate::Eighth),
+    (RateParam::Sixteenth, Rate::Sixteenth),
+    (RateParam::ThirtySecond, Rate::ThirtySecond),
+    (RateParam::QuarterTriplet, Rate::QuarterTriplet),
+    (RateParam::EighthTriplet, Rate::EighthTriplet),
+    (RateParam::SixteenthTriplet, Rate::SixteenthTriplet),
+];
+fn to_param(rate: Rate) -> RateParam {
+    RATES
+        .iter()
+        .find(|(_, r)| *r == rate)
+        .map_or(RateParam::Eighth, |(p, _)| *p)
+}
+fn linear(name: &str, v: f32, min: f32, max: f32, unit: &'static str) -> FloatParam {
+    FloatParam::new(name, v, FloatRange::Linear { min, max }).with_unit(unit)
+}
+/// Continuous controls, in the order of the gesture slots.
+pub const FLOATS: usize = 6;
+
+#[derive(Params)]
+pub struct BrazeParams {
+    #[persist = "editor"]
+    pub editor: Arc<EguiState>,
+    #[id = "source"]
+    pub source: EnumParam<SourceParam>,
+    #[nested(group = "Pitch")]
+    pub pitch: PitchParams,
+    #[id = "rate"]
+    pub rate: EnumParam<RateParam>,
+    #[id = "harmonic"]
+    pub harmonic: IntParam,
+    #[id = "depth"]
+    pub depth: FloatParam,
+    #[id = "low_cut"]
+    pub low_cut: FloatParam,
+    #[id = "width"]
+    pub width: FloatParam,
+    #[id = "phase"]
+    pub phase: FloatParam,
+    #[id = "gate"]
+    pub gate: FloatParam,
+    #[id = "snap"]
+    pub snap: BoolParam,
+    #[id = "output"]
+    pub output: FloatParam,
+    #[id = "bypass"]
+    pub bypass: BoolParam,
+}
+impl Default for BrazeParams {
+    fn default() -> Self {
+        let d = Settings::default();
+        Self {
+            editor: EguiState::from_size(braze_ui::WIDTH, braze_ui::HEIGHT),
+            source: EnumParam::new("Pitch source", SourceParam::Audio),
+            pitch: PitchParams::default(),
+            rate: EnumParam::new("Rate", to_param(d.rate)),
+            harmonic: IntParam::new(
+                "Harmonic",
+                d.harmonic as i32,
+                IntRange::Linear {
+                    min: 1,
+                    max: HARMONIC_MAX as i32,
+                },
+            ),
+            depth: linear("Depth", d.depth, 0., 100., " %"),
+            low_cut: FloatParam::new(
+                "Low cut",
+                d.low_cut,
+                FloatRange::Skewed {
+                    min: 0.,
+                    max: LOW_CUT_MAX,
+                    factor: FloatRange::skew_factor(-1.),
+                },
+            )
+            .with_unit(" Hz"),
+            width: linear("Width", d.width, 0., 100., " %"),
+            phase: linear("Phase", d.phase, 0., 360., "°"),
+            gate: linear("Gate", d.gate, -60., -20., " dB"),
+            snap: BoolParam::new("Snap to semitone", d.snap),
+            output: linear("Output", d.output, -12., 12., " dB"),
+            bypass: BoolParam::new("Bypass", false).make_bypass(),
+        }
+    }
+}
+impl BrazeParams {
+    pub fn settings(&self) -> Settings {
+        let rate = self.rate.value();
+        Settings {
+            source: self.source.value().into(),
+            pitch: self.pitch.pitch(),
+            rate: RATES
+                .iter()
+                .find(|(p, _)| *p == rate)
+                .map_or(Rate::Eighth, |(_, r)| *r),
+            harmonic: self.harmonic.value() as u32,
+            depth: self.depth.value(),
+            low_cut: self.low_cut.value(),
+            width: self.width.value(),
+            phase: self.phase.value(),
+            gate: self.gate.value(),
+            snap: self.snap.value(),
+            output: self.output.value(),
+            bypass: self.bypass.value(),
+        }
+    }
+    fn floats(&self) -> [&FloatParam; FLOATS] {
+        [
+            &self.depth,
+            &self.low_cut,
+            &self.width,
+            &self.phase,
+            &self.gate,
+            &self.output,
+        ]
+    }
+    fn values(s: &Settings) -> [f32; FLOATS] {
+        [s.depth, s.low_cut, s.width, s.phase, s.gate, s.output]
+    }
+    /// Pushes every changed editor value to the host. Continuous controls hold one gesture
+    /// while the pointer is down; switches are set in a single gesture.
+    pub fn apply(
+        &self,
+        setter: &ParamSetter,
+        old: &Settings,
+        new: &Settings,
+        dragging: bool,
+        open: &mut [bool; FLOATS],
+    ) {
+        let pairs = Self::values(old).into_iter().zip(Self::values(new));
+        for (i, (p, (a, b))) in self.floats().into_iter().zip(pairs).enumerate() {
+            if a != b {
+                if !open[i] {
+                    open[i] = true;
+                    setter.begin_set_parameter(p);
+                }
+                setter.set_parameter(p, b);
+            }
+            if !dragging && open[i] {
+                setter.end_set_parameter(p);
+                open[i] = false;
+            }
+        }
+        if new.harmonic != old.harmonic {
+            setter.begin_set_parameter(&self.harmonic);
+            setter.set_parameter(&self.harmonic, new.harmonic as i32);
+            setter.end_set_parameter(&self.harmonic);
+        }
+        if new.rate != old.rate {
+            setter.begin_set_parameter(&self.rate);
+            setter.set_parameter(&self.rate, to_param(new.rate));
+            setter.end_set_parameter(&self.rate);
+        }
+        for (p, a, b) in [
+            (&self.snap, old.snap, new.snap),
+            (&self.bypass, old.bypass, new.bypass),
+        ] {
+            if a != b {
+                setter.begin_set_parameter(p);
+                setter.set_parameter(p, b);
+                setter.end_set_parameter(p);
+            }
+        }
+        if new.source != old.source {
+            setter.begin_set_parameter(&self.source);
+            setter.set_parameter(&self.source, new.source.into());
+            setter.end_set_parameter(&self.source);
+        }
+        self.pitch.apply(setter, &old.pitch, &new.pitch);
+    }
+}
@@ -0,0 +1,216 @@
+//! Exercise the actual exported CLAP ABI without requiring a GUI or installed DAW.
+use clap_sys::{
+    audio_buffer::*,
+    events::*,
+    ext::{audio_ports::*, latency::*, state::*},
+    factory::plugin_factory::*,
+    host::*,
+    process::*,
+    stream::*,
+    version::*,
+};
+use std::{
+    ffi::{c_char, c_void, CStr},
+    io::{Cursor, Read},
+    ptr,
+};
+
+unsafe extern "C" fn extension(_: *const clap_host, _: *const c_char) -> *const c_void {
+    ptr::null()
+}
+unsafe extern "C" fn request(_: *const clap_host) {}
+unsafe extern "C" fn count(_: *const clap_input_events) -> u32 {
+    0
+}
+unsafe extern "C" fn event(_: *const clap_input_events, _: u32) -> *const clap_event_header {
+    ptr::null()
+}
+unsafe extern "C" fn push(_: *const clap_output_events, _: *const clap_event_header) -> bool {
+    true
+}
+unsafe extern "C" fn write(stream: *const clap_ostream, buffer: *const c_void, size: u64) -> i64 {
+    // SAFETY: The test owns the Vec for the entire synchronous save call.
+    let bytes = unsafe { &mut *((*stream).ctx as *mut Vec<u8>) };
+    bytes.extend_from_slice(unsafe {
+        std::slice::from_raw_parts(buffer as *const u8, size as usize)
+    });
+    size as i64
+}
+unsafe extern "C" fn read(stream: *const clap_istream, buffer: *mut c_void, size: u64) -> i64 {
+    // SAFETY: The test owns the Cursor; the wrapper supplies writable stream storage.
+    let cursor = unsafe { &mut *((*stream).ctx as *mut Cursor<Vec<u8>>) };
+    cursor
+        .read(unsafe { std::slice::from_raw_parts_mut(buffer as *mut u8, size as usize) })
+        .unwrap() as i64
+}
+
+#[test]
+fn effect_ports_state_latency_and_audio_lifecycle() {
+    // SAFETY: All callbacks, strings, streams, buffers, and the host outlive their
+    // synchronous ABI calls. Activation/processing/destruction follow CLAP order.
+    unsafe {
+        let entry = &braze::clap_entry;
+        assert!(entry.init.unwrap()(c"braze.clap".as_ptr()));
+        let factory = entry.get_factory.unwrap()(CLAP_PLUGIN_FACTORY_ID.as_ptr())
+            as *const clap_plugin_factory;
+        assert!(!factory.is_null());
+        let factory = &*factory;
+        assert_eq!(factory.get_plugin_count.unwrap()(factory), 1);
+        let descriptor = factory.get_plugin_descriptor.unwrap()(factory, 0);
+        assert!(!descriptor.is_null());
+        assert_eq!(CStr::from_ptr((*descriptor).name), c"Braze");
+        assert_eq!(
+            CStr::from_ptr((*descriptor).id),
+            c"io.narl.bass-foundry.braze"
+        );
+        assert!(factory.get_plugin_descriptor.unwrap()(factory, 1).is_null());
+        let host = clap_host {
+            clap_version: CLAP_VERSION,
+            host_data: ptr::null_mut(),
+            name: c"Storyboard test host".as_ptr(),
+            vendor: c"Tests".as_ptr(),
+            url: c"".as_ptr(),
+            version: c"1.0".as_ptr(),
+            get_extension: Some(extension),
+            request_restart: Some(request),
+            request_process: Some(request),
+            request_callback: Some(request),
+        };
+        let plugin = factory.create_plugin.unwrap()(factory, &host, (*descriptor).id);
+        assert!(!plugin.is_null());
+        let p = &*plugin;
+        assert!(p.init.unwrap()(plugin));
+        let ports = p.get_extension.unwrap()(plugin, CLAP_EXT_AUDIO_PORTS.as_ptr())
+            as *const clap_plugin_audio_ports;
+        assert!(!ports.is_null());
+        assert_eq!((*ports).count.unwrap()(plugin, false), 1);
+        assert_eq!((*ports).count.unwrap()(plugin, true), 1);
+        let latency = p.get_extension.unwrap()(plugin, CLAP_EXT_LATENCY.as_ptr())
+            as *const clap_plugin_latency;
+        assert!(!latency.is_null());
+        let state =
+            p.get_extension.unwrap()(plugin, CLAP_EXT_STATE.as_ptr()) as *const clap_plugin_state;
+        assert!(!state.is_null());
+        let state = &*state;
+        let save = || {
+            let mut bytes = Vec::new();
+            let stream = clap_ostream {
+                ctx: &mut bytes as *mut Vec<u8> as *mut c_void,
+                write: Some(write),
+            };
+            assert!(state.save.unwrap()(plugin, &stream));
+            bytes
+        };
+        let mut envelope: nih_plug::prelude::PluginState =
+            serde_json::from_slice(&save()[8..]).unwrap();
+        use nih_plug::wrapper::state::ParamValue;
+        // Depth 0 passes the input through the lookahead delay unchanged.
+        envelope.params.insert("depth".into(), ParamValue::F32(0.));
+        envelope.params.insert("width".into(), ParamValue::F32(40.));
+        envelope
+            .params
+            .insert("harmonic".into(), ParamValue::I32(3));
+        envelope
+            .params
+            .insert("rate".into(), ParamValue::String("1-16t".into()));
+        envelope
+            .params
+            .insert("snap".into(), ParamValue::Bool(true));
+        envelope
+            .params
+            .insert("source".into(), ParamValue::String("midi".into()));
+        let encoded = serde_json::to_vec(&envelope).unwrap();
+        let mut framed = (encoded.len() as u64).to_le_bytes().to_vec();
+        framed.extend_from_slice(&encoded);
+        let mut bytes = Cursor::new(framed);
+        let stream = clap_istream {
+            ctx: &mut bytes as *mut Cursor<Vec<u8>> as *mut c_void,
+            read: Some(read),
+        };
+        assert!(state.load.unwrap()(plugin, &stream));
+        let restored: nih_plug::prelude::PluginState =
+            serde_json::from_slice(&save()[8..]).unwrap();
+        assert_eq!(
+            serde_json::to_value(&restored.params).unwrap(),
+            serde_json::to_value(&envelope.params).unwrap()
+        );
+        for rate in [44100., 48000., 96000.] {
+            assert!(p.activate.unwrap()(plugin, rate, 1, 512));
+            let delay = (*latency).get.unwrap()(plugin) as usize;
+            // About 67 ms lookahead: two periods of the lowest detected note (30 Hz).
+            assert!((delay as f64 / rate - 0.067).abs() < 0.01, "{delay}");
+            assert!(p.start_processing.unwrap()(plugin));
+            let total = delay + 9600;
+            let mut position = 0;
+            let (mut energy_in, mut energy_out) = (0f64, 0f64);
+            while position < total {
+                let frames = [1, 127, 512, 31][position % 4].min(total - position);
+                // A 1 kHz tone at depth 0.
+                let tone = |n: usize| {
+                    0.25 * (std::f64::consts::TAU * 1000. * n as f64 / rate).sin() as f32
+                };
+                let mut input_left = [0f32; 512];
+                let mut input_right = [0f32; 512];
+                for i in 0..frames {
+                    input_left[i] = tone(position + i);
+                    input_right[i] = -tone(position + i);
+                }
+                let mut left = [0f32; 512];
+                let mut right = [0f32; 512];
+                let mut in_channels = [input_left.as_mut_ptr(), input_right.as_mut_ptr()];
+                let mut out_channels = [left.as_mut_ptr(), right.as_mut_ptr()];
+                let incoming = clap_audio_buffer {
+                    data32: in_channels.as_mut_ptr(),
+                    data64: ptr::null_mut(),
+                    channel_count: 2,
+                    latency: 0,
+                    constant_mask: 0,
+                };
+                let mut outgoing_audio = clap_audio_buffer {
+                    data32: out_channels.as_mut_ptr(),
+                    data64: ptr::null_mut(),
+                    channel_count: 2,
+                    latency: 0,
+                    constant_mask: 0,
+                };
+                let input = clap_input_events {
+                    ctx: ptr::null_mut(),
+                    size: Some(count),
+                    get: Some(event),
+                };
+                let outgoing = clap_output_events {
+                    ctx: ptr::null_mut(),
+                    try_push: Some(push),
+                };
+                let process = clap_process {
+                    steady_time: position as i64,
+                    frames_count: frames as u32,
+                    transport: ptr::null(),
+                    audio_inputs: &incoming,
+                    audio_outputs: &mut outgoing_audio,
+                    audio_inputs_count: 1,
+                    audio_outputs_count: 1,
+                    in_events: &input,
+                    out_events: &outgoing,
+                };
+                assert_ne!(p.process.unwrap()(plugin, &process), CLAP_PROCESS_ERROR);
+                for i in 0..frames {
+                    let n = position + i;
+                    if n < delay {
+                        assert!(left[i].abs() < 1e-6, "output before the lookahead");
+                    } else if n > delay + 4800 {
+                        energy_in += (tone(n - delay) as f64).powi(2);
+                        energy_out += (left[i] as f64).powi(2) + (right[i] as f64).powi(2);
+                    }
+                }
+                position += frames;
+            }
+            let ratio_db = 10. * (energy_out / (2. * energy_in)).log10();
+            assert!(ratio_db.abs() < 0.2, "{ratio_db}");
+            p.stop_processing.unwrap()(plugin);
+            p.deactivate.unwrap()(plugin);
+        }
+        p.destroy.unwrap()(plugin);
+        entry.deinit.unwrap()();
+    }
+}
@@ -0,0 +1,11 @@
+[package]
+name = "braze-ui"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+egui = "0.31.1"
+braze-core = { path = "../core" }
+common-ui = { path = "../../common/ui" }
+common-dsp = { path = "../../common/dsp" }
@@ -0,0 +1,422 @@
+//! Braze editor, shared by the CLAP wrapper and the headless renderer.
+use braze_core::{
+    cycles, envelope, AnalyzerFrame, Rate, Settings, Source, HARMONIC_MAX, LOW_CUT_MAX, LOW_CUT_OFF,
+};
+use common_ui::*;
+use egui::{self, Color32, FontId, Pos2, Rect, RichText, Sense, Stroke, Vec2};
+
+pub use common_ui::style;
+pub const WIDTH: u32 = 980;
+pub const HEIGHT: u32 = 716;
+
+pub struct State {
+    pub analyzer: AnalyzerFrame,
+    /// True while a pointer button is held, so knob drags become one host gesture.
+    pub gesture_active: bool,
+    pub help: String,
+    /// The advanced page shows its extra controls. Not saved.
+    pub advanced: bool,
+}
+impl Default for State {
+    fn default() -> Self {
+        Self {
+            analyzer: AnalyzerFrame::default(),
+            gesture_active: false,
+            advanced: false,
+            help: DEFAULT_HELP.into(),
+        }
+    }
+}
+const DEFAULT_HELP: &str =
+    "Put Braze on a reese or a layered bass. Pick the note value the beating should follow.";
+impl State {
+    pub fn accept_frame(&mut self, frame: AnalyzerFrame) {
+        self.analyzer = frame;
+    }
+}
+fn hint(r: &egui::Response, state: &mut State, text: &str) {
+    if r.hovered() || r.has_focus() {
+        state.help = text.into();
+    }
+}
+#[allow(clippy::too_many_arguments)]
+fn knob(
+    ui: &mut egui::Ui,
+    state: &mut State,
+    name: &str,
+    value: &mut f32,
+    range: std::ops::RangeInclusive<f32>,
+    default: f32,
+    unit: &str,
+    size: f32,
+    help: &str,
+) {
+    ui.vertical_centered(|ui| {
+        let r = rotary(ui, name, value, range, default, unit, size, ACCENT);
+        hint(&r, state, help);
+    });
+}
+
+/// Note value of one beat of harmonic `n`, as a label: "1/8", "1/16T", "1/8D", or "1/40".
+pub fn beat_label(s: &Settings, n: u32) -> String {
+    let quarters = s.rate.quarters() * s.harmonic as f64 / n as f64;
+    let per_whole = 4. / quarters;
+    for den in [1u32, 2, 4, 8, 16, 32, 64, 128] {
+        let d = den as f64;
+        if (per_whole - d).abs() < 1e-6 {
+            return format!("1/{den}");
+        }
+        if (per_whole - d * 1.5).abs() < 1e-6 {
+            return format!("1/{den}T");
+        }
+        if (per_whole - d / 1.5).abs() < 1e-6 {
+            return format!("1/{den}D");
+        }
+    }
+    if (per_whole - per_whole.round()).abs() < 1e-6 {
+        format!("1/{}", per_whole.round())
+    } else {
+        format!("{:.2} beats", quarters)
+    }
+}
+
+/// One bar of the beat of harmonics 1–8, with the beat grid and a playhead.
+fn beats(ui: &mut egui::Ui, settings: &Settings, frame: &AnalyzerFrame, height: f32) {
+    let (rect, _) = ui.allocate_exact_size(Vec2::new(ui.available_width(), height), Sense::hover());
+    let p = ui.painter_at(rect);
+    p.rect_filled(rect, 2., SCREEN);
+    let label_w = 86.;
+    let area = Rect::from_min_max(
+        rect.left_top() + Vec2::new(label_w, 26.),
+        rect.right_bottom() - Vec2::new(12., 10.),
+    );
+    p.text(
+        rect.left_top() + Vec2::new(10., 8.),
+        egui::Align2::LEFT_TOP,
+        "BEAT PER HARMONIC · ONE BAR",
+        FontId::proportional(11.),
+        MUTED,
+    );
+    p.text(
+        rect.right_top() + Vec2::new(-12., 8.),
+        egui::Align2::RIGHT_TOP,
+        if frame.synced {
+            format!("{:.1} BPM · host transport", frame.tempo)
+        } else {
+            format!("{:.1} BPM · free running", frame.tempo)
+        },
+        FontId::proportional(11.),
+        MUTED,
+    );
+    // Grid: every beat of the chosen rate, quarters brighter.
+    let step = settings.rate.quarters();
+    let mut q = 0f64;
+    while q < 4. - 1e-9 {
+        let x = area.left() + area.width() * (q / 4.) as f32;
+        let on_quarter = (q - q.round()).abs() < 1e-6;
+        let color = if on_quarter {
+            Color32::from_rgb(58, 62, 70)
+        } else {
+            Color32::from_rgb(32, 35, 40)
+        };
+        p.line_segment(
+            [Pos2::new(x, area.top()), Pos2::new(x, area.bottom())],
+            Stroke::new(1.0_f32, color),
+        );
+        q += step;
+    }
+    let rows = HARMONIC_MAX as usize;
+    let row_h = area.height() / rows as f32;
+    let depth = settings.depth * 0.01;
+    let points = 240;
+    let bar_start = (frame.beats / 4.).floor() * 4.;
+    for row in 0..rows {
+        let n = row as u32 + 1;
+        let top = area.top() + row_h * row as f32;
+        let chosen = n == settings.harmonic;
+        // Under the low cut the copy is removed: that harmonic keeps the bass's level.
+        let cut = settings.low_cut >= LOW_CUT_OFF
+            && frame.hz > 0.
+            && n as f32 * frame.hz < settings.low_cut;
+        let color = match (cut, chosen) {
+            (true, _) => DIM,
+            (false, true) => ACCENT,
+            (false, false) => STEEL,
+        };
+        p.text(
+            Pos2::new(rect.left() + 10., top + row_h * 0.5),
+            egui::Align2::LEFT_CENTER,
+            format!("H{n}"),
+            FontId::proportional(11.),
+            if chosen { ACCENT } else { MUTED },
+        );
+        p.text(
+            Pos2::new(rect.left() + 36., top + row_h * 0.5),
+            egui::Align2::LEFT_CENTER,
+            if cut {
+                "cut".to_string()
+            } else {
+                beat_label(settings, n)
+            },
+            FontId::monospace(11.),
+            if chosen { TEXT } else { DIM },
+        );
+        let line: Vec<Pos2> = (0..=points)
+            .map(|i| {
+                let t = i as f64 / points as f64;
+                let level = if cut {
+                    1.
+                } else {
+                    envelope(settings, n, cycles(settings, bar_start + 4. * t, 0), depth)
+                };
+                // 0 at the bottom of the row, twice the bass (√2 after correction) at the top.
+                let y = top + row_h * (0.92 - 0.8 * level / 2f32.sqrt());
+                Pos2::new(area.left() + area.width() * t as f32, y)
+            })
+            .collect();
+        p.add(egui::Shape::line(
+            line,
+            Stroke::new(if chosen { 2.0_f32 } else { 1.2_f32 }, color),
+        ));
+    }
+    let head = area.left() + area.width() * ((frame.beats - bar_start) / 4.) as f32;
+    p.line_segment(
+        [Pos2::new(head, area.top()), Pos2::new(head, area.bottom())],
+        Stroke::new(1.0_f32, Color32::from_rgba_unmultiplied(255, 255, 255, 90)),
+    );
+    p.rect_stroke(
+        rect,
+        2.,
+        Stroke::new(1.0_f32, EDGE),
+        egui::StrokeKind::Inside,
+    );
+}
+
+pub fn show(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
+    backdrop(ui);
+    state.help = DEFAULT_HELP.into();
+    state.gesture_active = ui.input(|i| i.pointer.any_down());
+    ui.add_space(2.);
+    let mut advanced = state.advanced;
+    header_paged(
+        ui,
+        "BRAZE",
+        "TEMPO-LOCKED BEATING",
+        Some(&mut advanced),
+        |ui| {
+            let r = ui
+                .selectable_label(settings.bypass, RichText::new("BYPASS").size(13.))
+                .on_hover_text("Crossfade to the delayed dry signal.");
+            if r.clicked() {
+                settings.bypass = !settings.bypass;
+            }
+            ui.separator();
+            let mut mode = settings.source.mode();
+            pitch_from(ui, &mut mode, &mut settings.pitch);
+            settings.source = Source::from_mode(mode);
+        },
+    );
+    state.advanced = advanced;
+    ui.add_space(6.);
+    let frame = state.analyzer;
+    ui.horizontal_top(|ui| {
+        panel(ui, |ui| {
+            ui.set_width(240.);
+            ui.set_min_height(TOP);
+            ui.vertical(|ui| note_panel(ui, settings, &frame));
+        });
+        ui.add_space(4.);
+        panel(ui, |ui| {
+            ui.set_width(ui.available_width());
+            beats(ui, settings, &frame, TOP);
+        });
+    });
+    ui.add_space(6.);
+    panel(ui, |ui| {
+        ui.set_width(ui.available_width());
+        ui.vertical(|ui| controls(ui, settings, state));
+    });
+    ui.separator();
+    ui.label(RichText::new(&state.help).color(MUTED));
+}
+const TOP: f32 = 300.;
+fn note_panel(ui: &mut egui::Ui, settings: &Settings, frame: &AnalyzerFrame) {
+    caption(ui, "NOTE");
+    let (name, hz) = match frame.note {
+        Some(n) if frame.hz > 0. => (common_dsp::note_name(n), format!("{:.1} Hz", frame.hz)),
+        _ => ("—".into(), "no note".into()),
+    };
+    ui.label(
+        RichText::new(name)
+            .font(FontId::new(54., egui::FontFamily::Name("medium".into())))
+            .color(if frame.note.is_some() { TEXT } else { DIM }),
+    );
+    ui.label(RichText::new(hz).monospace().size(14.).color(MUTED));
+    ui.add_space(14.);
+    let beat_hz = frame.tempo / 60. / settings.rate.quarters();
+    readout(
+        ui,
+        &format!("HARMONIC {} BEATS", settings.harmonic),
+        format!("{:.2} Hz, every {}", beat_hz, settings.rate.label()),
+        ACCENT,
+    );
+    if settings.low_cut >= LOW_CUT_OFF
+        && frame.hz > 0.
+        && settings.harmonic as f32 * frame.hz < settings.low_cut
+    {
+        ui.label(
+            RichText::new("Under Low cut on this note: it does not beat. Pick a higher harmonic.")
+                .size(12.)
+                .color(ACCENT),
+        );
+        ui.add_space(6.);
+    }
+    let cents = 1200. * frame.ratio.max(1e-6).log2();
+    readout(
+        ui,
+        "COPY DETUNE ON THIS NOTE",
+        if frame.hz > 0. {
+            format!("+{cents:.1} cents")
+        } else {
+            "waiting for a note".into()
+        },
+        TEXT,
+    );
+    ui.label(
+        RichText::new(format!(
+            "{:.0} ms lookahead · {}",
+            frame.latency as f32 / frame.sample_rate * 1000.,
+            pitch_status(settings.source.mode(), &settings.pitch)
+        ))
+        .size(12.)
+        .color(MUTED),
+    );
+}
+fn controls(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
+    let d = Settings::default();
+    ui.horizontal(|ui| {
+        caption(ui, "RATE");
+        ui.add_space(6.);
+        for rate in Rate::ALL {
+            let r =
+                ui.selectable_label(settings.rate == rate, RichText::new(rate.label()).size(13.));
+            if r.clicked() {
+                settings.rate = rate;
+            }
+            hint(
+                &r,
+                state,
+                "One beat cycle of the chosen harmonic lasts this note value, on every note.",
+            );
+        }
+        ui.add_space(18.);
+        caption(ui, "ON HARMONIC");
+        ui.add_space(6.);
+        for n in 1..=HARMONIC_MAX {
+            let r = ui.selectable_label(
+                settings.harmonic == n,
+                RichText::new(format!("{n}")).size(13.),
+            );
+            if r.clicked() {
+                settings.harmonic = n;
+            }
+            hint(
+                &r,
+                state,
+                "This harmonic beats at Rate. Harmonic n beats n/this times as fast. \
+                 Pick the harmonic you hear the movement on.",
+            );
+        }
+    });
+    ui.add_space(8.);
+    ui.separator();
+    let advanced = state.advanced;
+    ui.columns(if advanced { 6 } else { 4 }, |c| {
+        knob(
+            &mut c[0],
+            state,
+            "Depth",
+            &mut settings.depth,
+            0. ..=100.,
+            d.depth,
+            " %",
+            72.,
+            "Level of the detuned copy. 100 % beats down to full nulls; 0 % is the dry bass.",
+        );
+        knob(
+            &mut c[1],
+            state,
+            "Low cut",
+            &mut settings.low_cut,
+            0. ..=LOW_CUT_MAX,
+            d.low_cut,
+            " Hz",
+            72.,
+            "No copy below this frequency: the sub does not beat and keeps its level. \
+             Under 20 Hz the cut is off.",
+        );
+        knob(
+            &mut c[2],
+            state,
+            "Width",
+            &mut settings.width,
+            0. ..=100.,
+            d.width,
+            " %",
+            72.,
+            "Moves the right channel's beat against the left. 100 %: one side peaks while \
+             the other nulls. Check the mono sum.",
+        );
+        let at = if advanced {
+            knob(
+                &mut c[3],
+                state,
+                "Phase",
+                &mut settings.phase,
+                0. ..=360.,
+                d.phase,
+                "°",
+                72.,
+                "Where the beat peaks. 0° puts the peak of the chosen harmonic on the beat.",
+            );
+            knob(
+                &mut c[4],
+                state,
+                "Gate",
+                &mut settings.gate,
+                -60. ..=-20.,
+                d.gate,
+                " dB",
+                72.,
+                "Input level that counts as a note. Raise it if tails retrigger.",
+            );
+            5
+        } else {
+            3
+        };
+        knob(
+            &mut c[at],
+            state,
+            "Output",
+            &mut settings.output,
+            -12. ..=12.,
+            d.output,
+            " dB",
+            72.,
+            "Output trim.",
+        );
+    });
+    if state.advanced {
+        ui.add_space(4.);
+        let r = ui.selectable_label(settings.snap, RichText::new("SNAP TO SEMITONE").size(13.));
+        if r.clicked() {
+            settings.snap = !settings.snap;
+        }
+        hint(
+            &r,
+            state,
+            "Round the detected pitch. Off keeps the copy's jumps on the real period, which is \
+             seamless on detuned patches.",
+        );
+    }
+}
@@ -26,6 +26,7 @@
    },
    "packages": [
      "common-ui",
+      "common-dsp",
      "patina-core",
      "patina-ui",
      "patina-render"
@@ -130,5 +131,96 @@
      "knurl-core",
      "knurl-ui"
    ]
+  },
+  "planish": {
+    "name": "Planish",
+    "description": "Upward and downward compression in bands set by harmonic number, the same on every note",
+    "manifest": "plugins/planish/plugin/Cargo.toml",
+    "library": "planish",
+    "documentation": "docs/planish",
+    "clap_id": "io.narl.bass-foundry.planish",
+    "licenses": {
+      "plugins/common/ui/assets/OFL.txt": "licenses/Roboto-OFL.txt"
+    },
+    "packages": [
+      "common-ui",
+      "common-dsp",
+      "planish-core",
+      "planish-ui"
+    ]
+  },
+  "braze": {
+    "name": "Braze",
+    "description": "Adds a detuned copy whose beating stays on the tempo grid on every note",
+    "manifest": "plugins/braze/plugin/Cargo.toml",
+    "library": "braze",
+    "documentation": "docs/braze",
+    "clap_id": "io.narl.bass-foundry.braze",
+    "licenses": {
+      "plugins/common/ui/assets/OFL.txt": "licenses/Roboto-OFL.txt"
+    },
+    "packages": [
+      "common-ui",
+      "common-dsp",
+      "braze-core",
+      "braze-ui"
+    ]
+  },
+  "quench": {
+    "name": "Quench",
+    "description": "Clips the top as hard as you like while the sub passes clean",
+    "manifest": "plugins/quench/plugin/Cargo.toml",
+    "library": "quench",
+    "documentation": "docs/quench",
+    "clap_id": "io.narl.bass-foundry.quench",
+    "licenses": {
+      "plugins/common/ui/assets/OFL.txt": "licenses/Roboto-OFL.txt"
+    },
+    "packages": [
+      "common-ui",
+      "common-dsp",
+      "quench-core",
+      "quench-ui"
+    ]
+  },
+  "ballast": {
+    "name": "Ballast",
+    "description": "Levels every note or switch-up to one loudness with a single gain each",
+    "manifest": "plugins/ballast/plugin/Cargo.toml",
+    "library": "ballast",
+    "documentation": "docs/ballast",
+    "clap_id": "io.narl.bass-foundry.ballast",
+    "licenses": {
+      "plugins/common/ui/assets/OFL.txt": "licenses/Roboto-OFL.txt"
+    },
+    "packages": [
+      "common-ui",
+      "common-dsp",
+      "ballast-core",
+      "ballast-ui"
+    ]
+  },
+  "forge": {
+    "name": "Forge",
+    "description": "One tracked channel strip: Lathe, Temper and Knurl behind one note tracker, in any order",
+    "manifest": "plugins/forge/plugin/Cargo.toml",
+    "library": "forge",
+    "documentation": "docs/forge",
+    "clap_id": "io.narl.bass-foundry.forge",
+    "licenses": {
+      "plugins/common/ui/assets/OFL.txt": "licenses/Roboto-OFL.txt"
+    },
+    "packages": [
+      "common-ui",
+      "common-dsp",
+      "forge-core",
+      "forge-ui",
+      "lathe-core",
+      "lathe-ui",
+      "temper-core",
+      "temper-ui",
+      "knurl-core",
+      "knurl-ui"
+    ]
  }
 }
@@ -5,3 +5,4 @@ edition.workspace = true
 license.workspace = true

 [dependencies]
+serde = { workspace = true }
@@ -0,0 +1,118 @@
+//! Scores the note tracker on bass stems.
+//!
+//! ```text
+//! cargo run -p common-dsp --release --example tracker_report
+//! cargo run -p common-dsp --release --example tracker_report -- [--sub] [--bends]
+//!     [--note F1] [--key free|minor|major|root] stem.wav ...
+//! ```
+//! Without files it scores the synthetic corpus in `common_dsp::stems`, once with the stable
+//! default and once with Follow bends. With files, `--note` names the one note each file
+//! plays (for a wrong-note share); without it only note starts and unsure time are reported.
+use common_dsp::parse_note;
+use common_dsp::stems::{self, Score, Truth};
+use common_dsp::tracker::{PitchSource, Scale, TrackerConfig};
+use std::{env, fs, process};
+
+fn row(name: &str, s: Score) {
+    println!(
+        "{name:<14} {:>6.1}s {:>8.2} {:>8.2} {:>7.1}% {:>7.1}%",
+        s.seconds,
+        s.starts,
+        s.extra_starts,
+        s.wrong * 100.,
+        s.unsure * 100.
+    );
+}
+fn header() {
+    println!(
+        "{:<14} {:>7} {:>8} {:>8} {:>8} {:>8}",
+        "stem", "length", "starts/s", "extra/s", "wrong", "unsure"
+    );
+}
+
+fn main() {
+    let mut cfg = TrackerConfig::BASS;
+    let mut source = PitchSource::default();
+    let mut note = None;
+    let mut files = vec![];
+    let mut args = env::args().skip(1);
+    while let Some(a) = args.next() {
+        match a.as_str() {
+            "--sub" => cfg = TrackerConfig::SUB,
+            "--bends" => source.bends = true,
+            "--note" => {
+                let n = args.next().and_then(|n| parse_note(&n));
+                let Some(n) = n else {
+                    eprintln!("--note needs a note name such as F1");
+                    process::exit(2);
+                };
+                note = Some(n);
+                source.note = n;
+            }
+            "--key" => {
+                source.scale = match args.next().as_deref() {
+                    Some("free") => Scale::Free,
+                    Some("minor") => Scale::Minor,
+                    Some("major") => Scale::Major,
+                    Some("root") => Scale::Root,
+                    _ => {
+                        eprintln!("--key needs free, minor, major or root");
+                        process::exit(2);
+                    }
+                };
+            }
+            _ => files.push(a),
+        }
+    }
+    if files.is_empty() {
+        let rate = 48000.;
+        for bends in [false, true] {
+            println!(
+                "\n{}",
+                if bends {
+                    "Follow bends"
+                } else {
+                    "Stable (default)"
+                }
+            );
+            header();
+            let s = PitchSource { bends, ..source };
+            for stem in stems::all(rate) {
+                row(
+                    stem.name,
+                    stems::score(rate, cfg, s, &stem.samples, &stem.truth),
+                );
+            }
+        }
+        return;
+    }
+    header();
+    for path in files {
+        let wave = match fs::read(&path)
+            .map_err(|e| e.to_string())
+            .and_then(|b| common_dsp::wav::decode(&b).map_err(str::to_string))
+        {
+            Ok(w) => w,
+            Err(e) => {
+                eprintln!("{path}: {e}");
+                continue;
+            }
+        };
+        let channels = wave.channels as usize;
+        let mono: Vec<f32> = wave
+            .samples
+            .chunks(channels)
+            .map(|c| c.iter().sum::<f32>() / channels as f32)
+            .collect();
+        // With a known note, quiet samples are skipped rather than counted as silence.
+        let truth = match note {
+            Some(n) => vec![Truth::Note(n as f32); mono.len()],
+            None => vec![],
+        };
+        let name = path.rsplit('/').next().unwrap_or(&path);
+        row(
+            name,
+            stems::score(wave.rate as f32, cfg, source, &mono, &truth),
+        );
+    }
+}
@@ -1,6 +1,9 @@
-//! Shared allocation-free DSP building blocks: filters, pitch detection, notes, WAV files.
+//! Shared allocation-free DSP building blocks: filters, pitch detection, notes, WAV files,
+//! and synthetic test stems.
+pub mod loudness;
 pub mod meter;
 pub mod oversample;
+pub mod stems;
 pub mod svf;
 pub mod tracker;
 pub mod wav;
@@ -215,10 +218,39 @@ pub fn hz_to_midi(hz: f32) -> f32 {
 }
 /// Scientific note name: MIDI 60 = C4, 43.65 Hz = F1. FL Studio labels MIDI 60 as C5.
 pub fn note_name(note: u8) -> String {
+    note_name_spelled(note, false)
+}
+/// Note name with sharps, or with flats (Db, Eb, Gb, Ab, Bb) for keys written in flats.
+pub fn note_name_spelled(note: u8, flats: bool) -> String {
+    const SHARPS: [&str; 12] = [
+        "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B",
+    ];
+    const FLATS: [&str; 12] = [
+        "C", "Db", "D", "Eb", "E", "F", "Gb", "G", "Ab", "A", "Bb", "B",
+    ];
+    let names = if flats { FLATS } else { SHARPS };
+    format!("{}{}", names[note as usize % 12], note as i32 / 12 - 1)
+}
+/// Reads a scientific note name such as "F1" or "c#2", the inverse of [`note_name`].
+pub fn parse_note(text: &str) -> Option<u8> {
    const NAMES: [&str; 12] = [
        "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B",
    ];
-    format!("{}{}", NAMES[note as usize % 12], note as i32 / 12 - 1)
+    let text = text.trim();
+    let split = text.find(|c: char| c.is_ascii_digit() || c == '-')?;
+    let (pitch, octave) = text.split_at(split);
+    const FLATS: [&str; 12] = [
+        "C", "Db", "D", "Eb", "E", "F", "Gb", "G", "Ab", "A", "Bb", "B",
+    ];
+    let class = NAMES
+        .iter()
+        .position(|n| n.eq_ignore_ascii_case(pitch))
+        .or_else(|| FLATS.iter().position(|n| n.eq_ignore_ascii_case(pitch)))?
+        as i32;
+    let octave: i32 = octave.parse().ok()?;
+    u8::try_from((octave + 1) * 12 + class)
+        .ok()
+        .filter(|n| *n <= 127)
 }
 pub fn db_to_gain(db: f32) -> f32 {
    10f32.powf(db / 20.)
@@ -0,0 +1,71 @@
+//! ITU-R BS.1770 K-weighting: the pre-filter (a high shelf for the head) and the RLB high-pass.
+//! Mean square of the weighted signal, summed over channels, gives the loudness in LUFS as
+//! −0.691 + 10·log10(sum). Coefficients come from the standard's analog prototypes, so any
+//! sample rate is exact, not only 48 kHz.
+
+/// Biquad in transposed direct form II, in f64: the RLB pole sits close to 1 at high rates.
+#[derive(Clone, Copy, Debug, Default)]
+struct Stage {
+    b: [f64; 3],
+    a: [f64; 2],
+    z: [f64; 2],
+}
+impl Stage {
+    #[inline]
+    fn process(&mut self, x: f64) -> f64 {
+        let y = self.b[0] * x + self.z[0];
+        self.z[0] = self.b[1] * x - self.a[0] * y + self.z[1];
+        self.z[1] = self.b[2] * x - self.a[1] * y;
+        y
+    }
+}
+
+/// One channel of K-weighting. Allocation-free.
+#[derive(Clone, Copy, Debug)]
+pub struct KWeighting {
+    shelf: Stage,
+    high: Stage,
+}
+impl KWeighting {
+    pub fn new(rate: f32) -> Self {
+        let rate = rate as f64;
+        // Pre-filter: high shelf of about +4 dB above 1.7 kHz.
+        let (f0, g, q) = (1681.974450955533, 3.999843853973347, 0.7071752369554196);
+        let k = (std::f64::consts::PI * f0 / rate).tan();
+        let vh = 10f64.powf(g / 20.);
+        let vb = vh.powf(0.4996667741545416);
+        let a0 = 1. + k / q + k * k;
+        let shelf = Stage {
+            b: [
+                (vh + vb * k / q + k * k) / a0,
+                2. * (k * k - vh) / a0,
+                (vh - vb * k / q + k * k) / a0,
+            ],
+            a: [2. * (k * k - 1.) / a0, (1. - k / q + k * k) / a0],
+            z: [0.; 2],
+        };
+        // RLB: second-order high-pass at 38 Hz.
+        let (f0, q) = (38.13547087602444, 0.5003270373238773);
+        let k = (std::f64::consts::PI * f0 / rate).tan();
+        let a0 = 1. + k / q + k * k;
+        let high = Stage {
+            b: [1., -2., 1.],
+            a: [2. * (k * k - 1.) / a0, (1. - k / q + k * k) / a0],
+            z: [0.; 2],
+        };
+        Self { shelf, high }
+    }
+    #[inline]
+    pub fn process(&mut self, x: f32) -> f32 {
+        self.high.process(self.shelf.process(x as f64)) as f32
+    }
+    pub fn reset(&mut self) {
+        self.shelf.z = [0.; 2];
+        self.high.z = [0.; 2];
+    }
+}
+
+/// Loudness in LUFS of a mean square summed over channels.
+pub fn lufs(mean_square: f64) -> f32 {
+    (-0.691 + 10. * mean_square.max(1e-20).log10()) as f32
+}
@@ -0,0 +1,414 @@
+//! Synthetic bass stems with known notes, and a score for how well the tracker follows them.
+//!
+//! The stems imitate what makes real bass hard to track: FM growls, detuned reeses, moving
+//! formants over a weak fundamental, 808 slides, layered octaves and noise. They are a stand-in
+//! until real stems are collected; `examples/tracker_report.rs` scores real WAV files too.
+use crate::tracker::{NoteEvent, PitchSource, Tracker, TrackerConfig};
+use crate::{midi_to_hz, Biquad, Saw};
+use std::f32::consts::TAU;
+
+/// What the tracker should report for one input sample.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum Truth {
+    /// One note sounds at this fractional MIDI pitch.
+    Note(f32),
+    /// No note sounds; reporting one is wrong.
+    Silent,
+    /// A transition (attack, slide): not scored.
+    Skip,
+}
+
+pub struct Stem {
+    pub name: &'static str,
+    pub samples: Vec<f32>,
+    pub truth: Vec<Truth>,
+}
+
+/// Deterministic white noise in -1..1.
+struct Noise(u32);
+impl Noise {
+    fn sample(&mut self) -> f32 {
+        self.0 ^= self.0 << 13;
+        self.0 ^= self.0 >> 17;
+        self.0 ^= self.0 << 5;
+        self.0 as f32 / u32::MAX as f32 * 2. - 1.
+    }
+}
+
+/// Notes as (start s, end s, MIDI note). Samples outside every note are silent; the first
+/// `SKIP_S` of each note is not scored.
+const SKIP_S: f32 = 0.03;
+fn truth(rate: f32, len: usize, notes: &[(f32, f32, f32)]) -> Vec<Truth> {
+    (0..len)
+        .map(|i| {
+            let t = i as f32 / rate;
+            match notes.iter().find(|(a, b, _)| t >= *a && t < *b) {
+                Some((a, _, n)) if t - a >= SKIP_S => Truth::Note(*n),
+                Some(_) => Truth::Skip,
+                None => Truth::Silent,
+            }
+        })
+        .collect()
+}
+/// Short fade at note edges so onsets are clean.
+fn envelope(t: f32, a: f32, b: f32) -> f32 {
+    ((t - a) / 0.005).clamp(0., 1.) * ((b - t) / 0.005).clamp(0., 1.)
+}
+
+fn growl(rate: f32) -> Stem {
+    // FM: modulator at twice the carrier, index wobbling at 3 Hz, then driven.
+    let notes = [(0.1, 1.9, 29.), (2.0, 3.9, 32.)];
+    let len = (4. * rate) as usize;
+    let (mut pc, mut pm) = (0f32, 0f32);
+    let samples = (0..len)
+        .map(|i| {
+            let t = i as f32 / rate;
+            let Some(&(a, b, n)) = notes.iter().find(|(a, b, _)| t >= *a && t < *b) else {
+                return 0.;
+            };
+            let hz = midi_to_hz(n);
+            pc = (pc + hz / rate).fract();
+            pm = (pm + 2. * hz / rate).fract();
+            let index = 3. + 3. * (TAU * 3. * t).sin();
+            let x = (TAU * pc + index * (TAU * pm).sin()).sin();
+            0.5 * (2.5 * x).tanh() * envelope(t, a, b)
+        })
+        .collect();
+    Stem {
+        name: "growl",
+        samples,
+        truth: truth(rate, len, &notes),
+    }
+}
+
+fn hard_growl(rate: f32) -> Stem {
+    // FM at a 1:1 ratio, index sweeping 2–12 at 6 Hz, hard drive, then a sweeping resonance.
+    let notes = [(0.1, 1.0, 31.), (1.0, 2.0, 34.), (2.1, 3.9, 29.)];
+    let len = (4. * rate) as usize;
+    let (mut pc, mut pm) = (0f32, 0f32);
+    let mut band = Biquad::default();
+    let samples = (0..len)
+        .map(|i| {
+            let t = i as f32 / rate;
+            let Some(&(a, b, n)) = notes.iter().find(|(a, b, _)| t >= *a && t < *b) else {
+                return 0.;
+            };
+            if i % 32 == 0 {
+                let sweep = 0.5 + 0.5 * (TAU * 6. * t).sin();
+                band = retuned(band, Biquad::peak(rate, 200. + 1800. * sweep, 3., 12.));
+            }
+            let hz = midi_to_hz(n);
+            pc = (pc + hz / rate).fract();
+            pm = (pm + hz / rate).fract();
+            let index = 7. + 5. * (TAU * 6. * t).sin();
+            let x = (4. * (TAU * pc + index * (TAU * pm).sin()).sin()).tanh();
+            0.15 * band.process(x) * envelope(t, a, b)
+        })
+        .collect();
+    Stem {
+        name: "hard growl",
+        samples,
+        truth: truth(rate, len, &notes),
+    }
+}
+
+fn wobble(rate: f32) -> Stem {
+    // A saw on G1 through a resonant low-pass wobbling 80–1500 Hz at 1/8 notes of 140 BPM.
+    let notes = [(0.1, 3.9, 31.)];
+    let len = (4. * rate) as usize;
+    let mut saw = Saw::new(rate, midi_to_hz(31.));
+    let mut lp = [Biquad::default(); 2];
+    let samples = (0..len)
+        .map(|i| {
+            let t = i as f32 / rate;
+            let (a, b, _) = notes[0];
+            if t < a || t >= b {
+                return 0.;
+            }
+            if i % 32 == 0 {
+                let lfo = 0.5 - 0.5 * (TAU * (140. / 60. * 2.) * t).cos();
+                let hz = 80. * (1500f32 / 80.).powf(lfo);
+                lp[0] = retuned(lp[0], Biquad::lowpass(rate, hz, 6.));
+                lp[1] = retuned(lp[1], Biquad::lowpass(rate, hz, 0.7));
+            }
+            let y = lp[0].process(0.3 * saw.sample());
+            lp[1].process(y) * envelope(t, a, b)
+        })
+        .collect();
+    Stem {
+        name: "wobble",
+        samples,
+        truth: truth(rate, len, &notes),
+    }
+}
+
+fn reese(rate: f32) -> Stem {
+    // Two saws 12 cents apart, lowpassed; A1 then D2 legato.
+    let notes = [(0.1, 2.0, 33.), (2.0, 3.9, 38.)];
+    let len = (4. * rate) as usize;
+    let mut lp = [Biquad::lowpass(rate, 900., 0.7); 2];
+    let mut saws: Option<(f32, Saw, Saw)> = None;
+    let samples = (0..len)
+        .map(|i| {
+            let t = i as f32 / rate;
+            let Some(&(_, _, n)) = notes.iter().find(|(a, b, _)| t >= *a && t < *b) else {
+                return 0.;
+            };
+            if saws.as_ref().map(|s| s.0) != Some(n) {
+                let hz = midi_to_hz(n);
+                saws = Some((
+                    n,
+                    Saw::new(rate, hz * 2f32.powf(0.06 / 12.)),
+                    Saw::new(rate, hz * 2f32.powf(-0.06 / 12.)),
+                ));
+            }
+            let (_, a, b) = saws.as_mut().unwrap();
+            let x = 0.3 * (a.sample() + b.sample());
+            let y = lp[0].process(x);
+            let y = lp[1].process(y);
+            y * envelope(t, notes[0].0, notes[1].1)
+        })
+        .collect();
+    Stem {
+        name: "reese",
+        samples,
+        truth: truth(rate, len, &notes),
+    }
+}
+
+fn formant(rate: f32) -> Stem {
+    // A saw on E1 through two sweeping band-passes; the fundamental is 18 dB down.
+    let notes = [(0.1, 3.9, 28.)];
+    let len = (4. * rate) as usize;
+    let hz = midi_to_hz(28.);
+    let mut saw = Saw::new(rate, hz);
+    let mut phase = 0f32;
+    let mut bands = [Biquad::default(); 2];
+    let samples = (0..len)
+        .map(|i| {
+            let t = i as f32 / rate;
+            let (a, b, _) = notes[0];
+            if t < a || t >= b {
+                return 0.;
+            }
+            if i % 32 == 0 {
+                let sweep = 0.5 + 0.5 * (TAU * 1.5 * t).sin();
+                bands[0] = retuned(bands[0], Biquad::peak(rate, 300. + 500. * sweep, 4., 18.));
+                bands[1] = retuned(bands[1], Biquad::peak(rate, 900. + 900. * sweep, 4., 18.));
+            }
+            phase = (phase + hz / rate).fract();
+            let x = 0.05 * saw.sample();
+            let y = bands[0].process(x);
+            let y = bands[1].process(y);
+            (0.4 * y + 0.06 * (TAU * phase).sin()) * envelope(t, a, b)
+        })
+        .collect();
+    Stem {
+        name: "formant",
+        samples,
+        truth: truth(rate, len, &notes),
+    }
+}
+fn retuned(mut old: Biquad, new: Biquad) -> Biquad {
+    old.retune(new);
+    old
+}
+
+fn slide808(rate: f32) -> Stem {
+    // A saturated sine on C2 that slides down to G1 over 60 ms, decaying slowly.
+    let notes = [(0.1, 1.0, 36.), (1.0, 3.0, 31.)];
+    let len = (3.2 * rate) as usize;
+    let mut phase = 0f32;
+    let samples = (0..len)
+        .map(|i| {
+            let t = i as f32 / rate;
+            if !(0.1..3.0).contains(&t) {
+                return 0.;
+            }
+            let n = if t < 1. {
+                36.
+            } else {
+                36. - 5. * ((t - 1.) / 0.06).min(1.)
+            };
+            phase = (phase + midi_to_hz(n) / rate).fract();
+            let decay = (-(t - 0.1) / 2.5).exp();
+            0.6 * decay * (2. * (TAU * phase).sin()).tanh() * envelope(t, 0.1, 3.)
+        })
+        .collect();
+    let mut truth = truth(rate, len, &notes);
+    // The slide itself is not scored.
+    for (i, v) in truth.iter_mut().enumerate() {
+        let t = i as f32 / rate;
+        if (1.0..1.1).contains(&t) {
+            *v = Truth::Skip;
+        }
+    }
+    Stem {
+        name: "808 slide",
+        samples,
+        truth,
+    }
+}
+
+fn layered(rate: f32) -> Stem {
+    // Sub sine on F1 under an FM growl an octave up, plus noise: the drop's low end.
+    let notes = [(0.1, 3.9, 29.)];
+    let len = (4. * rate) as usize;
+    let hz = midi_to_hz(29.);
+    let (mut sub, mut pc, mut pm) = (0f32, 0f32, 0f32);
+    let mut noise = Noise(0x9e37_79b9);
+    let samples = (0..len)
+        .map(|i| {
+            let t = i as f32 / rate;
+            let (a, b, _) = notes[0];
+            if t < a || t >= b {
+                return 0.;
+            }
+            sub = (sub + hz / rate).fract();
+            pc = (pc + 2. * hz / rate).fract();
+            pm = (pm + 3. * hz / rate).fract();
+            let index = 2. + 2. * (TAU * 2. * t).sin();
+            let growl = (2. * (TAU * pc + index * (TAU * pm).sin()).sin()).tanh();
+            (0.3 * (TAU * sub).sin() + 0.35 * growl + 0.05 * noise.sample()) * envelope(t, a, b)
+        })
+        .collect();
+    Stem {
+        name: "layered",
+        samples,
+        truth: truth(rate, len, &notes),
+    }
+}
+
+fn riser(rate: f32) -> Stem {
+    // Low-passed noise swelling up: no note at all.
+    let len = (3. * rate) as usize;
+    let mut noise = Noise(0x1234_5678);
+    let mut lp = [Biquad::lowpass(rate, 600., 0.7); 2];
+    let samples = (0..len)
+        .map(|i| {
+            let t = i as f32 / rate;
+            let x = noise.sample() * 0.6 * (t / 3.);
+            let y = lp[0].process(x);
+            lp[1].process(y)
+        })
+        .collect();
+    Stem {
+        name: "noise riser",
+        samples,
+        truth: vec![Truth::Silent; len],
+    }
+}
+
+/// The corpus at sample rate `rate`.
+pub fn all(rate: f32) -> Vec<Stem> {
+    vec![
+        growl(rate),
+        hard_growl(rate),
+        wobble(rate),
+        reese(rate),
+        formant(rate),
+        slide808(rate),
+        layered(rate),
+        riser(rate),
+    ]
+}
+
+/// How the tracker did on one stem. Shares are of the scored samples.
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+pub struct Score {
+    pub seconds: f32,
+    /// Note starts per second beyond the stem's real notes (0 when no truth is known).
+    pub extra_starts: f32,
+    /// Note starts per second.
+    pub starts: f32,
+    /// Share of note samples where the tracker reports a sure note that is wrong by more
+    /// than half a semitone, plus silent samples where it reports a sure note.
+    pub wrong: f32,
+    /// Share of note samples where the tracker is unsure or reports no note.
+    pub unsure: f32,
+}
+
+/// Runs `samples` through a tracker and scores its output against `truth` (input-aligned;
+/// empty when unknown).
+pub fn score(
+    rate: f32,
+    cfg: TrackerConfig,
+    source: PitchSource,
+    samples: &[f32],
+    truth: &[Truth],
+) -> Score {
+    let mut t = Tracker::new(rate, cfg);
+    t.set(source);
+    let latency = t.latency();
+    let mut pitch = 0f32;
+    let mut starts = 0usize;
+    let (mut wrong, mut unsure, mut scored) = (0usize, 0usize, 0usize);
+    for i in 0..samples.len() + latency {
+        let x = samples.get(i).copied().unwrap_or(0.);
+        t.process(x, |e| match e {
+            NoteEvent::Start { pitch: p, .. } => {
+                pitch = p;
+                starts += 1;
+            }
+            NoteEvent::Move { pitch: p } => pitch = p,
+            NoteEvent::Stop => {}
+        });
+        let Some(at) = i.checked_sub(latency) else {
+            continue;
+        };
+        let sure = t.active();
+        match truth.get(at) {
+            Some(Truth::Note(n)) => {
+                scored += 1;
+                if !sure {
+                    unsure += 1;
+                } else if (pitch - n).abs() > 0.5 {
+                    wrong += 1;
+                }
+            }
+            Some(Truth::Silent) => {
+                scored += 1;
+                if sure {
+                    wrong += 1;
+                }
+            }
+            _ => {}
+        }
+    }
+    let seconds = samples.len() as f32 / rate;
+    let notes = count_notes(truth);
+    let share = |n: usize| {
+        if scored > 0 {
+            n as f32 / scored as f32
+        } else {
+            0.
+        }
+    };
+    Score {
+        seconds,
+        extra_starts: if truth.is_empty() {
+            0.
+        } else {
+            starts.saturating_sub(notes) as f32 / seconds
+        },
+        starts: starts as f32 / seconds,
+        wrong: share(wrong),
+        unsure: share(unsure),
+    }
+}
+/// Number of distinct notes in a truth track (a slide counts as a new note).
+fn count_notes(truth: &[Truth]) -> usize {
+    let mut last = None;
+    let mut n = 0;
+    for v in truth {
+        match v {
+            Truth::Note(p) if last != Some(*p) => {
+                n += 1;
+                last = Some(*p);
+            }
+            Truth::Silent => last = None,
+            _ => {}
+        }
+    }
+    n
+}
@@ -70,6 +70,21 @@ impl SvfCoef {
            m2: -1.,
        }
    }
+    /// Second-order allpass. With `q` = 1/√2 it has the phase of a Linkwitz–Riley crossover
+    /// built from two lowpass and two highpass stages at the same frequency, so it keeps
+    /// the bands of a crossover tree in phase.
+    pub fn allpass(rate: f32, hz: f32, q: f32) -> Self {
+        let k = 1. / q.max(1e-3);
+        let (a1, a2, a3) = Self::base(rate, hz, k, 1.);
+        Self {
+            a1,
+            a2,
+            a3,
+            m0: 1.,
+            m1: -2. * k,
+            m2: 0.,
+        }
+    }
    pub fn high_shelf(rate: f32, hz: f32, q: f32, gain_db: f32) -> Self {
        let a = 10f32.powf(gain_db / 40.);
        let k = 1. / q.max(1e-3);
@@ -3,7 +3,14 @@
 //! Detection runs on the undelayed input. Events are reported at *output* time, `latency()`
 //! samples later, so a host that delays its audio path by the same amount sees each note start
 //! exactly on its attack, with the pitch already known.
-use crate::{coefficient, gain_to_db, hz_to_midi, Biquad, Yin};
+//!
+//! Detection is built to stay put. A new note needs a confident pitch held for `NOTE_MS`
+//! (`OCTAVE_MS` for an octave jump), and inside a note the tuning only moves when the pitch
+//! drifts past `DEADBAND` for good. When the pitch reads keep disagreeing (FM growls, noise,
+//! formant sweeps), the tracker reports itself unsure: [`Tracker::active`] turns false, and
+//! tracked processing should fall back to something neutral rather than act on a guess.
+use crate::{coefficient, db_to_gain, gain_to_db, hz_to_midi, Biquad, Yin};
+use serde::{Deserialize, Serialize};

 const EVENTS: usize = 64;
 const HOP_MS: f32 = 5.;
@@ -12,6 +19,162 @@ const GATE_HYSTERESIS_DB: f32 = 6.;
 /// A pitch move this large (semitones) counts as a new note.
 const JUMP: f32 = 0.7;
 const CLARITY: f32 = 0.5;
+/// A different pitch must hold this long before it becomes the new note.
+const NOTE_MS: f32 = 40.;
+/// A jump down an octave must hold this long: octave errors are the commonest misread.
+const OCTAVE_MS: f32 = 80.;
+/// A jump up an octave must hold this long. A signal one octave up still repeats at the
+/// note's period, and detuned or FM basses read an octave up whenever their odd harmonics
+/// cancel, so these reads count as agreeing with the note.
+const OCTAVE_UP_MS: f32 = 200.;
+/// A new note's reads must stay within this spread (semitones): a swept resonance drags the
+/// reads along continuously, a real note change settles.
+const STEADY: f32 = 0.5;
+/// A note ends when the start of the analysis window (output time) stays this long below the
+/// gate's release level. Faster than the gate, whose envelope needs over 100 ms to fall.
+const QUIET_MS: f32 = 20.;
+/// Inside a note, the tuning moves only when the settled pitch is this far (semitones) off.
+const DEADBAND: f32 = 0.25;
+/// Per-hop step of the settled pitch towards each agreeing read.
+const SETTLE: f32 = 0.2;
+/// Trust kept per disagreeing read: about 40 ms of them make the note unsure.
+const TRUST_DISAGREE: f32 = 0.85;
+/// Trust kept per hop with no read: about 400 ms without one make the note unsure. Growls
+/// read only now and then, between stretches YIN cannot read at all.
+const TRUST_SILENT: f32 = 0.985;
+/// Share of the missing trust one agreeing read restores.
+const TRUST_AGREE: f32 = 0.5;
+const TRUST_LOST: f32 = 0.3;
+const TRUST_REGAINED: f32 = 0.6;
+
+/// Where notes come from.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Default)]
+pub enum PitchMode {
+    /// Pitch and note starts are detected from the audio.
+    #[default]
+    Audio,
+    /// Notes come from MIDI note input.
+    Midi,
+    /// Note starts come from the audio, the pitch is the fixed `note`: no detection at all.
+    Note,
+}
+
+/// Key lock for detected pitches. The root is the pitch class of [`PitchSource::note`].
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Default, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum Scale {
+    /// Any pitch, including between notes.
+    #[default]
+    Free,
+    /// Natural minor.
+    Minor,
+    Major,
+    /// Only the root, in any octave: detection picks the octave.
+    Root,
+}
+impl Scale {
+    fn steps(self) -> &'static [i32] {
+        match self {
+            Scale::Free => &[],
+            Scale::Minor => &[0, 2, 3, 5, 7, 8, 10],
+            Scale::Major => &[0, 2, 4, 5, 7, 9, 11],
+            Scale::Root => &[0],
+        }
+    }
+    /// The in-key note nearest `pitch`, or `pitch` itself when the scale is free.
+    pub fn snap(self, root: u8, pitch: f32) -> f32 {
+        let steps = self.steps();
+        if steps.is_empty() {
+            return pitch;
+        }
+        let root = (root % 12) as i32;
+        let base = pitch.round() as i32;
+        let mut best = base as f32;
+        let mut distance = f32::MAX;
+        for n in base - 7..=base + 7 {
+            if steps.contains(&(n - root).rem_euclid(12)) {
+                let d = (n as f32 - pitch).abs();
+                if d < distance {
+                    distance = d;
+                    best = n as f32;
+                }
+            }
+        }
+        best
+    }
+}
+
+/// The user's pitch-source choices, shared by every tracked plugin.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct PitchSource {
+    pub mode: PitchMode,
+    /// Detection threshold in dBFS for note starts (Audio and Note modes).
+    pub gate_db: f32,
+    /// Legato notes slide instead of restarting.
+    pub glide: bool,
+    /// The note played in Note mode (MIDI number); its pitch class is the key root.
+    pub note: u8,
+    pub scale: Scale,
+    /// Follow bends and vibrato on every hop and switch notes after 10 ms, as before 2026-11.
+    /// Fast, but it flickers on growls.
+    pub bends: bool,
+}
+impl Default for PitchSource {
+    fn default() -> Self {
+        Self {
+            mode: PitchMode::Audio,
+            gate_db: -42.,
+            glide: false,
+            note: DEFAULT_NOTE,
+            scale: Scale::Free,
+            bends: false,
+        }
+    }
+}
+/// F1, the commonest riddim root.
+pub const DEFAULT_NOTE: u8 = 29;
+/// Range of the Note control: C0 to C5.
+pub const NOTE_MIN: u8 = 12;
+pub const NOTE_MAX: u8 = 72;
+
+/// The stored part of a plugin's pitch source beside its mode and gate: Note mode's note, the
+/// key lock and Follow bends. Plugins keep it as one `pitch` field in their settings.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(deny_unknown_fields, default)]
+pub struct Pitch {
+    pub note: u8,
+    pub scale: Scale,
+    pub bends: bool,
+}
+impl Default for Pitch {
+    fn default() -> Self {
+        Self {
+            note: DEFAULT_NOTE,
+            scale: Scale::Free,
+            bends: false,
+        }
+    }
+}
+impl Pitch {
+    pub fn validate(&self) -> Result<(), &'static str> {
+        if (NOTE_MIN..=NOTE_MAX).contains(&self.note) {
+            Ok(())
+        } else {
+            Err("Note out of range")
+        }
+    }
+    /// The full tracker settings for `mode`, a gate threshold in dBFS and legato slides.
+    pub fn source(self, mode: PitchMode, gate_db: f32, glide: bool) -> PitchSource {
+        PitchSource {
+            mode,
+            gate_db,
+            glide,
+            note: self.note,
+            scale: self.scale,
+            bends: self.bends,
+        }
+    }
+}

 #[derive(Clone, Copy, Debug, PartialEq)]
 pub struct TrackerConfig {
@@ -40,6 +203,40 @@ impl TrackerConfig {
    };
 }

+/// The tracker's note state at one output sample.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
+pub struct NoteState {
+    /// A note sounds.
+    pub sounding: bool,
+    /// The sounding note's pitch is trusted ([`Tracker::active`]); false while none sounds.
+    pub sure: bool,
+}
+impl NoteState {
+    /// A note sounds but its pitch is not trusted: tracked processing should step back.
+    pub fn unsure(self) -> bool {
+        self.sounding && !self.sure
+    }
+}
+
+/// Latches "step back" across note ends: a module goes neutral while its note is unsure and
+/// returns only on a sure note, so a tail after an unsure stretch stays neutral too.
+#[derive(Clone, Copy, Debug, Default)]
+pub struct Fallback {
+    neutral: bool,
+}
+impl Fallback {
+    /// Updates from this sample's note state; true while the module should sound neutral.
+    pub fn neutral(&mut self, note: NoteState) -> bool {
+        if note.sounding {
+            self.neutral = !note.sure;
+        }
+        self.neutral
+    }
+    pub fn reset(&mut self) {
+        self.neutral = false;
+    }
+}
+
 #[derive(Clone, Copy, Debug, PartialEq)]
 pub enum NoteEvent {
    /// A new note. `glide` asks to slide from the previous pitch instead of restarting.
@@ -67,14 +264,50 @@ struct Event {
    kind: Kind,
 }

+/// A pitch that may become the next note.
+#[derive(Clone, Copy, Debug)]
+struct Candidate {
+    mean: f32,
+    low: f32,
+    high: f32,
+    reads: u32,
+}
+impl Candidate {
+    fn new(p: f32) -> Self {
+        Self {
+            mean: p,
+            low: p,
+            high: p,
+            reads: 1,
+        }
+    }
+    /// Adds a read, or returns None when it does not fit this candidate.
+    fn add(self, p: f32) -> Option<Self> {
+        let (low, high) = (self.low.min(p), self.high.max(p));
+        (high - low < STEADY).then(|| Self {
+            mean: self.mean + (p - self.mean) / (self.reads + 1) as f32,
+            low,
+            high,
+            reads: self.reads + 1,
+        })
+    }
+}
+
+/// One analysis window's result.
+#[derive(Clone, Copy, Debug)]
+enum Read {
+    Pitch(f32),
+    /// Sound YIN cannot read: no evidence either way.
+    Unclear,
+    Silent,
+}
+
 /// Allocation-free after `new`. Pitches are fractional MIDI notes.
 pub struct Tracker {
    rate: f32,
    cfg: TrackerConfig,
    latency: usize,
-    midi: bool,
-    gate_db: f32,
-    glide: bool,
+    source: PitchSource,
    detect: [Biquad; 2],
    decimate: usize,
    decimate_count: usize,
@@ -85,6 +318,9 @@ pub struct Tracker {
    yin: Yin,
    hop: usize,
    hop_count: usize,
+    note_hops: u32,
+    octave_hops: u32,
+    octave_up_hops: u32,
    gate_env: f32,
    gate_release: f32,
    gate_open: bool,
@@ -96,8 +332,17 @@ pub struct Tracker {
    /// Output-time note state.
    sounding: bool,
    pending: bool,
+    /// The note ended on silence while the gate stayed open: the next sound starts a note.
+    rest: bool,
+    quiet_hops: u32,
+    quiet_need: u32,
    tracked: f32,
-    candidate: Option<(f32, u8)>,
+    /// Running pitch of the agreeing reads inside the note.
+    settled: f32,
+    candidate: Option<Candidate>,
+    /// 1 while reads agree with the note, falling towards 0 while they do not.
+    trust: f32,
+    sure: bool,
    held: [u8; 16],
    held_len: usize,
 }
@@ -110,13 +355,13 @@ impl Tracker {
        // YIN needs one comparison window of at least the longest period after the lags.
        let analysis = 2 * max_lag + 3;
        let q = std::f32::consts::FRAC_1_SQRT_2;
+        let hop = ((detect_rate * HOP_MS * 0.001) as usize).max(1);
+        let hop_ms = hop as f32 / detect_rate * 1000.;
        Self {
            rate,
            cfg,
            latency: analysis * decimate,
-            midi: false,
-            gate_db: -42.,
-            glide: false,
+            source: PitchSource::default(),
            detect: [Biquad::lowpass(rate, cfg.detect_lowpass, q); 2],
            decimate,
            decimate_count: 0,
@@ -125,8 +370,11 @@ impl Tracker {
            ring_at: 0,
            scratch: vec![0.; analysis],
            yin: Yin::new(max_lag + 2),
-            hop: ((detect_rate * HOP_MS * 0.001) as usize).max(1),
+            hop,
            hop_count: 0,
+            note_hops: (NOTE_MS / hop_ms).round().max(2.) as u32,
+            octave_hops: (OCTAVE_MS / hop_ms).round().max(2.) as u32,
+            octave_up_hops: (OCTAVE_UP_MS / hop_ms).round().max(2.) as u32,
            gate_env: 0.,
            gate_release: 1. - coefficient(rate, 30.),
            gate_open: false,
@@ -140,8 +388,14 @@ impl Tracker {
            event_len: 0,
            sounding: false,
            pending: false,
+            rest: false,
+            quiet_hops: 0,
+            quiet_need: (QUIET_MS / hop_ms).round().max(1.) as u32,
            tracked: 0.,
+            settled: 0.,
            candidate: None,
+            trust: 0.,
+            sure: false,
            held: [0; 16],
            held_len: 0,
        }
@@ -153,22 +407,28 @@ impl Tracker {
    pub fn config(&self) -> TrackerConfig {
        self.cfg
    }
-    /// `midi` selects note input over detection; `gate_db` is the detection threshold;
-    /// `glide` lets legato notes slide. Returns true when the source changed, which drops
-    /// every pending and held note: the caller should release its sound.
-    pub fn set(&mut self, midi: bool, gate_db: f32, glide: bool) -> bool {
-        let changed = midi != self.midi;
-        self.midi = midi;
-        self.gate_db = gate_db;
-        self.glide = glide;
+    pub fn source(&self) -> PitchSource {
+        self.source
+    }
+    /// Applies the pitch-source choices. Returns true when the mode changed, which drops every
+    /// pending and held note: the caller should release its sound.
+    pub fn set(&mut self, source: PitchSource) -> bool {
+        let changed = source.mode != self.source.mode;
+        self.source = source;
        if changed {
            self.release_all();
        }
        changed
    }
+    fn midi(&self) -> bool {
+        self.source.mode == PitchMode::Midi
+    }
    fn release_all(&mut self) {
        self.sounding = false;
        self.pending = false;
+        self.rest = false;
+        self.quiet_hops = 0;
+        self.sure = false;
        self.held_len = 0;
        self.event_len = 0;
        self.candidate = None;
@@ -192,10 +452,22 @@ impl Tracker {
    pub fn note_off(&mut self, note: u8) {
        self.push(Kind::NoteOff(note.min(127)));
    }
-    /// True while a note sounds at output time.
+    /// True while a note sounds at output time, sure or not.
    pub fn sounding(&self) -> bool {
        self.sounding
    }
+    /// True while tracked processing should act: a note sounds and its pitch is trusted.
+    /// MIDI and Note modes are always sure; detection is unsure from an onset until a pitch
+    /// reads, and while reads keep disagreeing with the note.
+    pub fn active(&self) -> bool {
+        self.sounding && (self.source.mode != PitchMode::Audio || self.sure)
+    }
+    pub fn state(&self) -> NoteState {
+        NoteState {
+            sounding: self.sounding,
+            sure: self.active(),
+        }
+    }
    fn push(&mut self, kind: Kind) {
        if self.event_len == EVENTS {
            // Dropping the oldest keeps the newest note state; overflow only happens on floods.
@@ -209,45 +481,81 @@ impl Tracker {
        };
        self.event_len += 1;
    }
-    /// Detected pitch of the most recent analysis window, in fractional MIDI notes.
-    fn estimate(&mut self) -> Option<f32> {
+    /// Detected pitch of the most recent analysis window, in fractional MIDI notes, snapped to
+    /// the key when one is set.
+    fn estimate(&mut self) -> Read {
        let n = self.ring.len();
        for i in 0..n {
            self.scratch[i] = self.ring[(self.ring_at + i) % n];
        }
-        let (hz, clarity) = self.yin.estimate(
+        // The window starts at output time: a quiet head means the note has ended there.
+        let head = self.hop.min(n);
+        let power = self.scratch[..head].iter().map(|v| v * v).sum::<f32>() / head as f32;
+        let quiet = db_to_gain(self.source.gate_db - GATE_HYSTERESIS_DB);
+        if power < quiet * quiet {
+            return Read::Silent;
+        }
+        let s = self.source;
+        match self.yin.estimate(
            &self.scratch,
            self.detect_rate,
            self.cfg.min_hz,
            self.cfg.max_hz,
-        )?;
-        (clarity >= CLARITY).then(|| hz_to_midi(hz))
+        ) {
+            Some((hz, clarity)) if clarity >= CLARITY => {
+                Read::Pitch(s.scale.snap(s.note, hz_to_midi(hz)))
+            }
+            _ => Read::Unclear,
+        }
    }
    fn start(&mut self, pitch: f32, glide: bool, emit: &mut impl FnMut(NoteEvent)) {
        self.tracked = pitch;
+        self.settled = pitch;
        self.candidate = None;
        self.pending = false;
        self.sounding = true;
+        self.trust = 1.;
+        self.sure = true;
        emit(NoteEvent::Start { pitch, glide });
    }
    fn stop(&mut self, emit: &mut impl FnMut(NoteEvent)) {
+        let was = self.sounding || self.pending;
        self.sounding = false;
        self.pending = false;
+        self.sure = false;
+        self.quiet_hops = 0;
        self.candidate = None;
-        emit(NoteEvent::Stop);
+        if was {
+            emit(NoteEvent::Stop);
+        }
+    }
+    /// A note starts at output time from `read`: detected (or pending until a pitch reads) in
+    /// Audio mode, the set note in Note mode.
+    fn onset(&mut self, read: Read, emit: &mut impl FnMut(NoteEvent)) {
+        self.rest = false;
+        self.quiet_hops = 0;
+        match (self.source.mode, read) {
+            (PitchMode::Note, _) => self.start(self.source.note as f32, false, emit),
+            (_, Read::Pitch(p)) => self.start(p, false, emit),
+            _ => {
+                self.pending = true;
+                self.sounding = true;
+                self.sure = false;
+                self.trust = 0.;
+            }
+        }
    }
    fn handle(&mut self, kind: Kind, emit: &mut impl FnMut(NoteEvent)) {
-        let midi = self.midi;
-        match kind {
-            Kind::Onset if !midi => match self.estimate() {
-                Some(p) => self.start(p, false, emit),
-                None => {
-                    self.pending = true;
-                    self.sounding = true;
-                }
-            },
-            Kind::Release if !midi => self.stop(emit),
-            Kind::NoteOn(n) if midi => {
+        match (self.source.mode, kind) {
+            (PitchMode::Audio | PitchMode::Note, Kind::Onset) => {
+                let read = self.estimate();
+                self.onset(read, emit);
+            }
+            (PitchMode::Audio | PitchMode::Note, Kind::Release) => {
+                self.rest = false;
+                self.stop(emit);
+            }
+            (PitchMode::Midi, Kind::NoteOn(n)) => {
                let len = self.held_len;
                if let Some(i) = self.held[..len].iter().position(|h| *h == n) {
                    self.held.copy_within(i + 1..len, i);
@@ -260,9 +568,9 @@ impl Tracker {
                let legato = self.held_len > 0;
                self.held[self.held_len] = n;
                self.held_len += 1;
-                self.start(n as f32, legato && self.glide, emit);
+                self.start(n as f32, legato && self.source.glide, emit);
            }
-            Kind::NoteOff(n) if midi => {
+            (PitchMode::Midi, Kind::NoteOff(n)) => {
                let len = self.held_len;
                let Some(i) = self.held[..len].iter().position(|h| *h == n) else {
                    return;
@@ -274,48 +582,119 @@ impl Tracker {
                    self.stop(emit);
                } else if top {
                    let next = self.held[self.held_len - 1];
-                    self.start(next as f32, self.glide, emit);
+                    self.start(next as f32, self.source.glide, emit);
                }
            }
            _ => {}
        }
    }
+    /// Moves the trust score one hop: `Some(true)` for a read that agrees with the note,
+    /// `Some(false)` for one that does not, `None` for no read. Hysteresis on `sure`.
+    fn trust(&mut self, agree: Option<bool>) {
+        match agree {
+            Some(true) => self.trust += (1. - self.trust) * TRUST_AGREE,
+            Some(false) => self.trust *= TRUST_DISAGREE,
+            None => self.trust *= TRUST_SILENT,
+        }
+        if self.sure && self.trust < TRUST_LOST {
+            self.sure = false;
+        } else if !self.sure && self.trust > TRUST_REGAINED {
+            self.sure = true;
+        }
+    }
    /// Regular analysis; its window starts at the current output time.
    fn hop_analysis(&mut self, emit: &mut impl FnMut(NoteEvent)) {
-        if self.midi || !self.sounding {
+        if self.midi() || !(self.sounding || self.rest) {
            return;
        }
-        let Some(p) = self.estimate() else {
-            return;
-        };
-        if self.pending {
-            self.start(p, false, emit);
-            return;
-        }
-        if (p - self.tracked).abs() >= JUMP {
-            match self.candidate {
-                Some((c, count)) if (c - p).abs() < 0.5 => {
-                    if count + 1 >= 2 {
-                        self.start(p, self.glide, emit);
-                    } else {
-                        self.candidate = Some((p, count + 1));
-                    }
+        let read = self.estimate();
+        if let Read::Silent = read {
+            if self.sounding && !self.pending {
+                self.quiet_hops += 1;
+                if self.quiet_hops >= self.quiet_need {
+                    self.stop(emit);
+                    self.rest = true;
+                } else {
+                    self.trust(Some(false));
                }
-                _ => self.candidate = Some((p, 1)),
+            }
+            return;
+        }
+        self.quiet_hops = 0;
+        if self.rest {
+            return self.onset(read, emit);
+        }
+        if self.source.mode == PitchMode::Note {
+            return;
+        }
+        if self.pending {
+            if let Read::Pitch(p) = read {
+                self.start(p, false, emit);
+            }
+            return;
+        }
+        let p = match read {
+            Read::Pitch(p) => p,
+            Read::Unclear => return self.trust(None),
+            Read::Silent => unreachable!(),
+        };
+        let offset = p - self.tracked;
+        if offset.abs() < JUMP {
+            self.candidate = None;
+            self.trust(Some(true));
+            if self.source.bends {
+                self.tracked += 0.3 * offset;
+                emit(NoteEvent::Move {
+                    pitch: self.tracked,
+                });
+            } else {
+                self.settled += SETTLE * (p - self.settled);
+                if (self.settled - self.tracked).abs() >= DEADBAND {
+                    self.tracked = self.settled;
+                    emit(NoteEvent::Move {
+                        pitch: self.tracked,
+                    });
+                }
+            }
+            return;
+        }
+        let octaves = (offset / 12.).round();
+        let octave = octaves != 0. && (offset - 12. * octaves).abs() < JUMP;
+        let up = octave && octaves > 0.;
+        let candidate = if self.source.bends {
+            // The 0.1 rule: two reads within half a semitone.
+            match self.candidate {
+                Some(c) if (c.mean - p).abs() < 0.5 => Candidate {
+                    mean: p,
+                    reads: c.reads + 1,
+                    ..c
+                },
+                _ => Candidate::new(p),
            }
        } else {
-            self.candidate = None;
-            self.tracked += 0.3 * (p - self.tracked);
-            emit(NoteEvent::Move {
-                pitch: self.tracked,
-            });
+            self.candidate
+                .and_then(|c| c.add(p))
+                .unwrap_or(Candidate::new(p))
+        };
+        let need = match (self.source.bends, octave, up) {
+            (true, _, _) => 2,
+            (false, false, _) => self.note_hops,
+            (false, true, false) => self.octave_hops,
+            (false, true, true) => self.octave_up_hops,
+        };
+        if candidate.reads >= need {
+            let pitch = if self.source.bends { p } else { candidate.mean };
+            self.start(pitch, self.source.glide, emit);
+        } else {
+            self.candidate = Some(candidate);
+            self.trust(Some(up && !self.source.bends));
        }
    }
    /// Feeds one undelayed mono input sample. Events due at output time go to `emit`, in order.
    pub fn process(&mut self, mono: f32, mut emit: impl FnMut(NoteEvent)) {
        let d = self.detect[0].process(mono);
        let d = self.detect[1].process(d);
-        if !self.midi {
+        if !self.midi() {
            let a = d.abs();
            self.gate_env = if a > self.gate_env {
                a
@@ -323,13 +702,14 @@ impl Tracker {
                self.gate_env * self.gate_release
            };
            let level = gain_to_db(self.gate_env);
-            if level > self.gate_db {
+            let gate = self.source.gate_db;
+            if level > gate {
                self.gate_hold = (self.rate * GATE_HOLD_MS * 0.001) as usize;
                if !self.gate_open {
                    self.gate_open = true;
                    self.push(Kind::Onset);
                }
-            } else if self.gate_open && level < self.gate_db - GATE_HYSTERESIS_DB {
+            } else if self.gate_open && level < gate - GATE_HYSTERESIS_DB {
                if self.gate_hold == 0 {
                    self.gate_open = false;
                    self.push(Kind::Release);
@@ -397,3 +777,56 @@ impl PitchFollower {
        self.hz
    }
 }
+
+/// A processor driven by note events that are aligned with its input audio. Lathe, Temper and
+/// Knurl are built from one each, so the same code runs standalone (after its own tracker) and
+/// inside a strip that shares one tracker between several of them.
+pub trait Tracked {
+    /// Delay of the output behind the input, in samples.
+    fn latency(&self) -> usize;
+    /// The undelayed input, one tracker lookahead ahead of the audio passed to `process`.
+    /// Called before the sample's events.
+    fn ahead(&mut self, _mono: f32) {}
+    /// A note event due at the next `process` sample.
+    fn event(&mut self, e: NoteEvent);
+    /// One sample of audio and the tracker's note state at it. While the note is unsure
+    /// (see [`Fallback`]) the module should step back to something neutral.
+    fn process(&mut self, x: [f32; 2], note: NoteState) -> [f32; 2];
+}
+
+/// A tracker and the lookahead delay in front of one [`Tracked`] module: the standalone form.
+pub struct Lookahead {
+    pub tracker: Tracker,
+    delay: Vec<[f32; 2]>,
+    at: usize,
+}
+impl Lookahead {
+    pub fn new(rate: f32, cfg: TrackerConfig) -> Self {
+        let tracker = Tracker::new(rate, cfg);
+        let len = tracker.latency() + 1;
+        Self {
+            tracker,
+            delay: vec![[0.; 2]; len],
+            at: 0,
+        }
+    }
+    /// The tracker's lookahead, in samples.
+    pub fn latency(&self) -> usize {
+        self.tracker.latency()
+    }
+    pub fn reset(&mut self) {
+        self.tracker.reset();
+        self.delay.fill([0.; 2]);
+    }
+    /// Feeds one input sample (`mono` is its channel average) and returns `module`'s output.
+    #[inline]
+    pub fn process(&mut self, x: [f32; 2], mono: f32, module: &mut impl Tracked) -> [f32; 2] {
+        module.ahead(mono);
+        self.tracker.process(mono, |e| module.event(e));
+        let len = self.delay.len();
+        self.delay[self.at] = x;
+        self.at = (self.at + 1) % len;
+        let y = self.delay[self.at];
+        module.process(y, self.tracker.state())
+    }
+}
@@ -1,7 +1,7 @@
 use common_dsp::meter::HarmonicMeter;
 use common_dsp::oversample::Oversampler;
 use common_dsp::svf::{Svf, SvfCoef};
-use common_dsp::tracker::{NoteEvent, Tracker, TrackerConfig};
+use common_dsp::tracker::{NoteEvent, PitchMode, PitchSource, Scale, Tracker, TrackerConfig};
 use common_dsp::{hz_to_midi, Saw};
 use std::f32::consts::TAU;

@@ -46,6 +46,31 @@ fn svf_bell_at_zero_db_is_an_exact_identity() {
    }
 }

+#[test]
+fn svf_allpass_matches_a_linkwitz_riley_split() {
+    let q = std::f32::consts::FRAC_1_SQRT_2;
+    let (low, high, all) = (
+        SvfCoef::lowpass(RATE, 300., q),
+        SvfCoef::highpass(RATE, 300., q),
+        SvfCoef::allpass(RATE, 300., q),
+    );
+    let mut s = [Svf::default(); 5];
+    let mut saw = Saw::new(RATE, 55.);
+    for _ in 0..9600 {
+        let x = saw.sample();
+        let l = s[0].process(&low, x);
+        let l = s[1].process(&low, l);
+        let h = s[2].process(&high, x);
+        let h = s[3].process(&high, h);
+        let a = s[4].process(&all, x);
+        assert!((l + h - a).abs() < 1e-4, "{} vs {a}", l + h);
+    }
+    let mut s = Svf::default();
+    for hz in [30., 300., 3000.] {
+        assert!(sine_gain(|x| s.process(&all, x), hz).abs() < 0.01);
+    }
+}
+
 #[test]
 fn svf_survives_retuning_every_sample() {
    let mut s = Svf::default();
@@ -149,7 +174,7 @@ fn harmonic_meter_reads_saw_harmonics() {
 #[test]
 fn tracker_reports_notes_at_output_time() {
    let mut t = Tracker::new(RATE, TrackerConfig::BASS);
-    t.set(false, -42., false);
+    t.set(PitchSource::default());
    let l = t.latency();
    assert!(l < (0.08 * RATE) as usize, "{l}");
    let onset = 4800;
@@ -185,7 +210,11 @@ fn tracker_reports_notes_at_output_time() {
 #[test]
 fn tracker_delays_midi_by_the_latency() {
    let mut t = Tracker::new(RATE, TrackerConfig::BASS);
-    assert!(t.set(true, -42., true));
+    assert!(t.set(PitchSource {
+        mode: PitchMode::Midi,
+        glide: true,
+        ..PitchSource::default()
+    }));
    let l = t.latency();
    let mut events = vec![];
    for i in 0..l + 2000 {
@@ -223,3 +252,129 @@ fn tracker_delays_midi_by_the_latency() {
        ]
    );
 }
+
+#[test]
+fn stable_tracker_holds_its_notes_on_the_stem_corpus() {
+    let stable = PitchSource::default();
+    let bends = PitchSource {
+        bends: true,
+        ..stable
+    };
+    let (mut extra_stable, mut extra_bends) = (0., 0.);
+    for stem in common_dsp::stems::all(RATE) {
+        let s = common_dsp::stems::score(
+            RATE,
+            TrackerConfig::BASS,
+            stable,
+            &stem.samples,
+            &stem.truth,
+        );
+        let b =
+            common_dsp::stems::score(RATE, TrackerConfig::BASS, bends, &stem.samples, &stem.truth);
+        assert!(s.extra_starts <= 0.25, "{}: {s:?}", stem.name);
+        assert!(s.wrong <= 0.05, "{}: {s:?}", stem.name);
+        assert!(s.wrong <= b.wrong + 0.005, "{}: {s:?} vs {b:?}", stem.name);
+        extra_stable += s.extra_starts;
+        extra_bends += b.extra_starts;
+    }
+    // Follow bends keeps the fast 0.1 behaviour, which flickers on formant basses.
+    assert!(
+        extra_bends > 10. * extra_stable.max(1.),
+        "{extra_stable} vs {extra_bends}"
+    );
+}
+
+#[test]
+fn tracker_turns_inactive_when_reads_stop_agreeing() {
+    let mut t = Tracker::new(RATE, TrackerConfig::BASS);
+    t.set(PitchSource::default());
+    let mut saw = Saw::new(RATE, 55.);
+    let mut seed = 1u32;
+    let mut active = vec![];
+    for i in 0..(RATE * 1.5) as usize {
+        seed ^= seed << 13;
+        seed ^= seed >> 17;
+        seed ^= seed << 5;
+        let noise = seed as f32 / u32::MAX as f32 - 0.5;
+        let x = if i < 24000 { 0.5 * saw.sample() } else { noise };
+        t.process(x, |_| {});
+        active.push(t.active());
+    }
+    let l = t.latency();
+    assert!(active[l + 12000..l + 23000].iter().all(|a| *a));
+    // Unreadable sound is no evidence against the note, so trust fades slowly: growls read
+    // only now and then. Within half a second of noise, tracked processing stops acting.
+    assert!(active[l + 48000..].iter().all(|a| !*a));
+}
+
+#[test]
+fn note_mode_plays_the_set_note_on_each_onset() {
+    let mut t = Tracker::new(RATE, TrackerConfig::BASS);
+    t.set(PitchSource {
+        mode: PitchMode::Note,
+        note: 29,
+        ..PitchSource::default()
+    });
+    let mut saw = Saw::new(RATE, 220.);
+    let mut events = vec![];
+    for i in 0..48000 {
+        let x = if (4800..20000).contains(&i) || i >= 30000 {
+            0.5 * saw.sample()
+        } else {
+            0.
+        };
+        t.process(x, |e| events.push(e));
+        if i == 15000 {
+            assert!(t.active());
+        }
+    }
+    let starts: Vec<_> = events
+        .iter()
+        .filter_map(|e| match e {
+            NoteEvent::Start { pitch, .. } => Some(*pitch),
+            _ => None,
+        })
+        .collect();
+    assert_eq!(starts, vec![29., 29.]);
+    assert!(!events.iter().any(|e| matches!(e, NoteEvent::Move { .. })));
+}
+
+#[test]
+fn key_lock_snaps_reads_to_the_scale() {
+    // F minor: F G Ab Bb C Db Eb. F#1 (30) leans to G1 when read sharp.
+    assert_eq!(Scale::Minor.snap(29, 30.4), 31.);
+    assert_eq!(Scale::Minor.snap(29, 29.6), 29.);
+    assert_eq!(Scale::Major.snap(0, 61.), 60.);
+    assert_eq!(Scale::Root.snap(29, 40.6), 41.);
+    assert_eq!(Scale::Root.snap(29, 35.4), 41.);
+    assert_eq!(Scale::Free.snap(29, 30.37), 30.37);
+}
+
+#[test]
+fn key_lock_keeps_a_drifting_wobble_on_its_root() {
+    let stem = common_dsp::stems::all(RATE)
+        .into_iter()
+        .find(|s| s.name == "wobble")
+        .unwrap();
+    let free = PitchSource::default();
+    let root = PitchSource {
+        note: 31,
+        scale: Scale::Root,
+        ..free
+    };
+    let f = common_dsp::stems::score(RATE, TrackerConfig::BASS, free, &stem.samples, &stem.truth);
+    let r = common_dsp::stems::score(RATE, TrackerConfig::BASS, root, &stem.samples, &stem.truth);
+    assert!(r.unsure + r.wrong < f.unsure + f.wrong, "{f:?} vs {r:?}");
+    assert!(r.wrong <= 0.02, "{r:?}");
+}
+
+#[test]
+fn note_names_parse_back() {
+    for n in 0..=127u8 {
+        assert_eq!(common_dsp::parse_note(&common_dsp::note_name(n)), Some(n));
+    }
+    assert_eq!(common_dsp::parse_note(" f1 "), Some(29));
+    assert_eq!(common_dsp::note_name_spelled(30, true), "Gb1");
+    assert_eq!(common_dsp::parse_note("Gb1"), Some(30));
+    assert_eq!(common_dsp::parse_note("H2"), None);
+}
@@ -80,3 +80,29 @@ fn wave_round_trip_keeps_root_and_wavetable_chunks() {
    assert_eq!(wav::decode(&bytes).unwrap(), w);
    assert!(wav::decode(&bytes[..40]).is_err());
 }
+
+#[test]
+fn k_weighting_reads_a_full_scale_997_hz_sine_at_minus_3_lufs() {
+    use common_dsp::loudness::{lufs, KWeighting};
+    let level = |rate: f32, hz: f64| {
+        let mut k = KWeighting::new(rate);
+        let n = rate as usize;
+        let mut sum = 0f64;
+        for i in 0..2 * n {
+            let x = (std::f64::consts::TAU * hz * i as f64 / rate as f64).sin() as f32;
+            let y = k.process(x) as f64;
+            if i >= n {
+                sum += y * y;
+            }
+        }
+        lufs(sum / n as f64)
+    };
+    // BS.1770-4: a 0 dBFS 997 Hz sine in one channel reads −3.01 LKFS, at every rate.
+    for rate in [44100., 48000., 96000., 192000.] {
+        let got = level(rate, 997.);
+        // BS.1770 allows meters 0.1 LU; the prototypes land within 0.03 up to 192 kHz.
+        assert!((got + 3.01).abs() < 0.05, "{rate}: {got}");
+    }
+    // The RLB high-pass counts a 30 Hz sub much less than the mids.
+    assert!(level(48000., 30.) < level(48000., 997.) - 5.);
+}
@@ -0,0 +1,9 @@
+[package]
+name = "common-params"
+version = "0.1.0"
+edition = "2021"
+license = "ISC"
+
+[dependencies]
+nih_plug = { git = "https://github.com/robbert-vdh/nih-plug.git", rev = "de421011f41a6d10fc8c7a6084e4f4dee0143683", default-features = false }
+common-dsp = { path = "../dsp" }
@@ -0,0 +1,121 @@
+//! Host parameters shared by every tracked plugin: Note mode's note, the key lock and
+//! Follow bends. Plugins nest [`PitchParams`] in their own parameter struct.
+use common_dsp::tracker::{Pitch, Scale, NOTE_MAX, NOTE_MIN};
+use common_dsp::note_name;
+use nih_plug::prelude::*;
+use std::sync::Arc;
+
+#[derive(Enum, Debug, PartialEq, Eq, Clone, Copy)]
+pub enum ScaleParam {
+    #[id = "free"]
+    #[name = "Off"]
+    Free,
+    #[id = "minor"]
+    Minor,
+    #[id = "major"]
+    Major,
+    #[id = "root"]
+    #[name = "Root only"]
+    Root,
+}
+impl From<ScaleParam> for Scale {
+    fn from(s: ScaleParam) -> Self {
+        match s {
+            ScaleParam::Free => Scale::Free,
+            ScaleParam::Minor => Scale::Minor,
+            ScaleParam::Major => Scale::Major,
+            ScaleParam::Root => Scale::Root,
+        }
+    }
+}
+impl From<Scale> for ScaleParam {
+    fn from(s: Scale) -> Self {
+        match s {
+            Scale::Free => ScaleParam::Free,
+            Scale::Minor => ScaleParam::Minor,
+            Scale::Major => ScaleParam::Major,
+            Scale::Root => ScaleParam::Root,
+        }
+    }
+}
+
+#[derive(Params)]
+pub struct PitchParams {
+    /// The note played in Note mode; its pitch class is the key root.
+    #[id = "note"]
+    pub note: IntParam,
+    #[id = "scale"]
+    pub scale: EnumParam<ScaleParam>,
+    #[id = "bends"]
+    pub bends: BoolParam,
+}
+impl Default for PitchParams {
+    fn default() -> Self {
+        let d = Pitch::default();
+        Self {
+            note: IntParam::new(
+                "Note",
+                d.note as i32,
+                IntRange::Linear {
+                    min: NOTE_MIN as i32,
+                    max: NOTE_MAX as i32,
+                },
+            )
+            .with_value_to_string(Arc::new(|v| note_name(v.clamp(0, 127) as u8)))
+            .with_string_to_value(Arc::new(|s| parse_note(s).map(i32::from))),
+            scale: EnumParam::new("Key lock", ScaleParam::Free),
+            bends: BoolParam::new("Follow bends", d.bends),
+        }
+    }
+}
+impl PitchParams {
+    pub fn pitch(&self) -> Pitch {
+        Pitch {
+            note: (self.note.value().clamp(NOTE_MIN as i32, NOTE_MAX as i32)) as u8,
+            scale: self.scale.value().into(),
+            bends: self.bends.value(),
+        }
+    }
+    /// Pushes editor changes to the host, one gesture per change.
+    pub fn apply(&self, setter: &ParamSetter, old: &Pitch, new: &Pitch) {
+        if old.note != new.note {
+            setter.begin_set_parameter(&self.note);
+            setter.set_parameter(&self.note, new.note as i32);
+            setter.end_set_parameter(&self.note);
+        }
+        if old.scale != new.scale {
+            setter.begin_set_parameter(&self.scale);
+            setter.set_parameter(&self.scale, new.scale.into());
+            setter.end_set_parameter(&self.scale);
+        }
+        if old.bends != new.bends {
+            setter.begin_set_parameter(&self.bends);
+            setter.set_parameter(&self.bends, new.bends);
+            setter.end_set_parameter(&self.bends);
+        }
+    }
+}
+
+/// Reads a note name such as "F1" within the Note range.
+pub fn parse_note(text: &str) -> Option<u8> {
+    common_dsp::parse_note(text).filter(|n| (NOTE_MIN..=NOTE_MAX).contains(n))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn note_names_round_trip() {
+        for n in NOTE_MIN..=NOTE_MAX {
+            assert_eq!(parse_note(&note_name(n)), Some(n));
+        }
+        assert_eq!(parse_note("f1"), Some(29));
+        assert_eq!(parse_note("H2"), None);
+    }
+    #[test]
+    fn scale_maps_both_ways() {
+        for s in [Scale::Free, Scale::Minor, Scale::Major, Scale::Root] {
+            assert_eq!(Scale::from(ScaleParam::from(s)), s);
+        }
+    }
+}
@@ -6,3 +6,4 @@ license.workspace = true

 [dependencies]
 egui = "0.31.1"
+common-dsp = { path = "../dsp" }
@@ -1,4 +1,6 @@
 //! Shared hardware look for every plugin editor: palette, fonts, knobs, panels.
+use common_dsp::note_name;
+use common_dsp::tracker::{Pitch, PitchMode, Scale, NOTE_MAX, NOTE_MIN};
 use egui::{self, Color32, FontId, Pos2, Rect, RichText, Sense, Stroke, Vec2};

 // Dark anodized hardware: graphite surfaces, one signal colour, steel data traces.
@@ -113,6 +115,58 @@ pub fn rotary(
    unit: &str,
    size: f32,
    color: Color32,
+) -> egui::Response {
+    let response = dial(ui, value, range.clone(), default, size, color);
+    dial_caption(ui, name, size);
+    ui.add(
+        egui::DragValue::new(value)
+            .range(range)
+            .speed(0.1)
+            .suffix(unit),
+    );
+    response
+}
+/// A rotary whose value field shows custom text, for values that are not a plain number
+/// with a unit (a ratio, a mapped knob position).
+#[allow(clippy::too_many_arguments)]
+pub fn rotary_text(
+    ui: &mut egui::Ui,
+    name: &str,
+    value: &mut f32,
+    range: std::ops::RangeInclusive<f32>,
+    default: f32,
+    size: f32,
+    color: Color32,
+    format: impl Fn(f32) -> String,
+    parse: impl Fn(&str) -> Option<f32>,
+) -> egui::Response {
+    let response = dial(ui, value, range.clone(), default, size, color);
+    dial_caption(ui, name, size);
+    let speed = (*range.end() - *range.start()) as f64 / 200.;
+    ui.add(
+        egui::DragValue::new(value)
+            .range(range)
+            .speed(speed)
+            .custom_formatter(|v, _| format(v as f32))
+            .custom_parser(|s| parse(s).map(f64::from)),
+    );
+    response
+}
+fn dial_caption(ui: &mut egui::Ui, name: &str, size: f32) {
+    ui.label(
+        RichText::new(name.to_uppercase())
+            .size(if size > 100. { 14. } else { 12. })
+            .color(MUTED),
+    );
+}
+/// The knob itself: drag, keys, double-click reset, and drawing.
+fn dial(
+    ui: &mut egui::Ui,
+    value: &mut f32,
+    range: std::ops::RangeInclusive<f32>,
+    default: f32,
+    size: f32,
+    color: Color32,
 ) -> egui::Response {
    let low = *range.start();
    let high = *range.end();
@@ -212,17 +266,6 @@ pub fn rotary(
    if response.has_focus() {
        p.circle_stroke(center, radius + 2., Stroke::new(1.0_f32, color));
    }
-    ui.label(
-        RichText::new(name.to_uppercase())
-            .size(if size > 100. { 14. } else { 12. })
-            .color(MUTED),
-    );
-    ui.add(
-        egui::DragValue::new(value)
-            .range(range)
-            .speed(0.1)
-            .suffix(unit),
-    );
    response
 }
 /// Vertical gradient rectangle, used for panel faces.
@@ -269,6 +312,16 @@ pub fn readout(ui: &mut egui::Ui, label: &str, value: String, color: Color32) {
 }
 /// Product header: accent mark, product name, subtitle, then right-aligned controls.
 pub fn header(ui: &mut egui::Ui, name: &str, subtitle: &str, right: impl FnOnce(&mut egui::Ui)) {
+    header_paged(ui, name, subtitle, None, right);
+}
+/// Product header with the MAIN / ADVANCED page switch after the subtitle.
+pub fn header_paged(
+    ui: &mut egui::Ui,
+    name: &str,
+    subtitle: &str,
+    advanced: Option<&mut bool>,
+    right: impl FnOnce(&mut egui::Ui),
+) {
    ui.horizontal(|ui| {
        let (mark, _) = ui.allocate_exact_size(Vec2::new(4., 26.), Sense::hover());
        ui.painter().rect_filled(mark, 1., ACCENT);
@@ -278,6 +331,10 @@ pub fn header(ui: &mut egui::Ui, name: &str, subtitle: &str, right: impl FnOnce(
                .color(TEXT),
        );
        ui.label(RichText::new(subtitle).size(12.).color(MUTED));
+        if let Some(advanced) = advanced {
+            ui.add_space(14.);
+            page_switch(ui, advanced);
+        }
        ui.with_layout(egui::Layout::right_to_left(egui::Align::Center), right);
    });
 }
@@ -318,3 +375,219 @@ pub fn meter(ui: &mut egui::Ui, label: &str, db: f32, color: Color32, width: f32
        );
    });
 }
+
+const PITCH_CLASSES: [&str; 12] = [
+    "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B",
+];
+fn scale_name(scale: Scale) -> &'static str {
+    match scale {
+        Scale::Free => "off",
+        Scale::Minor => "minor",
+        Scale::Major => "major",
+        Scale::Root => "root only",
+    }
+}
+/// Short status of the pitch source for readout lines: "detecting pitch in F minor".
+pub fn pitch_status(mode: PitchMode, pitch: &Pitch) -> String {
+    match (mode, pitch.scale) {
+        (PitchMode::Audio, Scale::Free) => "detecting pitch".into(),
+        (PitchMode::Audio, s) => format!(
+            "detecting pitch, key {} {}",
+            PITCH_CLASSES[pitch.note as usize % 12],
+            scale_name(s)
+        ),
+        (PitchMode::Midi, _) => "following MIDI".into(),
+        (PitchMode::Note, _) => format!("fixed on {}", note_name(pitch.note)),
+    }
+}
+/// Pitch source switch for a header's right-to-left row: AUDIO, MIDI and NOTE, then a button
+/// that opens Note mode's note, or the key lock and Follow bends for detection.
+pub fn pitch_from(ui: &mut egui::Ui, mode: &mut PitchMode, pitch: &mut Pitch) {
+    let id = ui.make_persistent_id("pitch-detail");
+    let detail = match *mode {
+        PitchMode::Note => Some(note_name(pitch.note)),
+        PitchMode::Audio => Some(match pitch.scale {
+            Scale::Free if pitch.bends => "BENDS".into(),
+            Scale::Free => "KEY OFF".into(),
+            s => format!(
+                "{} {}",
+                PITCH_CLASSES[pitch.note as usize % 12],
+                match s {
+                    Scale::Minor => "MIN",
+                    Scale::Major => "MAJ",
+                    _ => "ROOT",
+                }
+            ),
+        }),
+        PitchMode::Midi => None,
+    };
+    if let Some(detail) = detail {
+        let help = if *mode == PitchMode::Note {
+            "The note this plugin follows. Nothing is detected: set the drop's root."
+        } else {
+            "Key lock and Follow bends for detection."
+        };
+        let r = ui
+            .button(RichText::new(detail).size(13.).color(ACCENT))
+            .on_hover_text(help);
+        if r.clicked() {
+            ui.memory_mut(|m| m.toggle_popup(id));
+        }
+        let note_mode = *mode == PitchMode::Note;
+        egui::popup_below_widget(
+            ui,
+            id,
+            &r,
+            egui::PopupCloseBehavior::CloseOnClickOutside,
+            |ui| {
+                ui.set_min_width(220.);
+                if note_mode {
+                    pitch_note(ui, pitch, true);
+                } else {
+                    caption(ui, "KEY LOCK");
+                    ui.horizontal(|ui| {
+                        for s in [Scale::Free, Scale::Minor, Scale::Major, Scale::Root] {
+                            let help = match s {
+                                Scale::Free => "Any pitch, also between notes.",
+                                Scale::Minor => "Only notes of the natural minor scale.",
+                                Scale::Major => "Only notes of the major scale.",
+                                Scale::Root => "Only the root: detection picks the octave.",
+                            };
+                            let label = RichText::new(scale_name(s).to_uppercase()).size(12.);
+                            if ui
+                                .selectable_label(pitch.scale == s, label)
+                                .on_hover_text(help)
+                                .clicked()
+                            {
+                                pitch.scale = s;
+                            }
+                        }
+                    });
+                    if pitch.scale != Scale::Free {
+                        ui.add_space(4.);
+                        caption(ui, "ROOT");
+                        pitch_note(ui, pitch, false);
+                    }
+                    ui.add_space(6.);
+                    ui.checkbox(&mut pitch.bends, "Follow bends").on_hover_text(
+                        "Retune on every bend and switch notes within 10 ms. Fast, but it \
+                         flickers on growls. Off holds each note until a new one is clear.",
+                    );
+                }
+            },
+        );
+    }
+    for (m, label, help) in [
+        (
+            PitchMode::Note,
+            "NOTE",
+            "You set the note; the audio only starts and stops it. Nothing is detected.",
+        ),
+        (
+            PitchMode::Midi,
+            "MIDI",
+            "Notes from MIDI input. In FL, set the channel's MIDI output port and this \
+             effect's input port to the same number.",
+        ),
+        (
+            PitchMode::Audio,
+            "AUDIO",
+            "Detect the pitch from the audio. When detection is unsure, tracked processing \
+             steps back instead of guessing.",
+        ),
+    ] {
+        let r = ui
+            .selectable_label(*mode == m, RichText::new(label).size(13.))
+            .on_hover_text(help);
+        if r.clicked() {
+            *mode = m;
+        }
+    }
+    caption(ui, "PITCH FROM");
+}
+/// Twelve pitch-class buttons, and octave steps when `octave` is set.
+fn pitch_note(ui: &mut egui::Ui, pitch: &mut Pitch, octave: bool) {
+    let class = pitch.note % 12;
+    let base = pitch.note - class;
+    for row in [0..6, 6..12] {
+        ui.horizontal(|ui| {
+            for c in row {
+                let r = ui.add_sized(
+                    [30., 22.],
+                    egui::SelectableLabel::new(class == c as u8, PITCH_CLASSES[c]),
+                );
+                if r.clicked() {
+                    pitch.note = (base + c as u8).clamp(NOTE_MIN, NOTE_MAX);
+                }
+            }
+        });
+    }
+    if octave {
+        ui.horizontal(|ui| {
+            caption(ui, "OCTAVE");
+            if ui.button("−").clicked() && pitch.note >= NOTE_MIN + 12 {
+                pitch.note -= 12;
+            }
+            ui.label(
+                RichText::new(format!("{}", pitch.note as i32 / 12 - 1))
+                    .monospace()
+                    .color(TEXT),
+            );
+            if ui.button("+").clicked() && pitch.note + 12 <= NOTE_MAX {
+                pitch.note += 12;
+            }
+            ui.label(RichText::new(note_name(pitch.note)).color(ACCENT));
+        });
+    }
+}
+
+/// MAIN / ADVANCED page switch. The main page holds the few controls a first result needs;
+/// the advanced page holds everything else. Returns true while the advanced page shows.
+pub fn page_switch(ui: &mut egui::Ui, advanced: &mut bool) -> bool {
+    ui.horizontal(|ui| {
+        for (page, label, help) in [
+            (
+                false,
+                "MAIN",
+                "The controls that matter for a first result.",
+            ),
+            (true, "ADVANCED", "Every control, for fine tuning."),
+        ] {
+            let r = ui
+                .selectable_label(*advanced == page, RichText::new(label).size(12.))
+                .on_hover_text(help);
+            if r.clicked() {
+                *advanced = page;
+            }
+        }
+    });
+    *advanced
+}
+/// Choice drawn as large chips, centred, for a plugin's mode on its main page.
+pub fn choice<T: PartialEq + Copy>(
+    ui: &mut egui::Ui,
+    value: &mut T,
+    options: &[(T, &str, &str)],
+) -> Option<egui::Response> {
+    let mut hovered = None;
+    let n = options.len() as f32;
+    let width = n * 96. + (n - 1.) * ui.spacing().item_spacing.x;
+    ui.horizontal(|ui| {
+        ui.add_space(((ui.available_width() - width) / 2.).max(0.));
+        for (v, label, help) in options {
+            let r = ui
+                .add_sized(
+                    [96., 30.],
+                    egui::SelectableLabel::new(*value == *v, RichText::new(*label).size(14.)),
+                )
+                .on_hover_text(*help);
+            if r.clicked() {
+                *value = *v;
+            }
+            if r.hovered() {
+                hovered = Some(r);
+            }
+        }
+    });
+    hovered
+}
@@ -1,7 +1,7 @@
 //! Writes a take as ready-to-use files: the full loop, one file per slice and a wavetable.
 use crate::settings::Settings;
 use crate::take::{render, wavetable, Take, TABLE};
-use common_dsp::{note_name, wav};
+use common_dsp::wav;
 use std::path::{Path, PathBuf};

 #[derive(Debug, Clone, PartialEq)]
@@ -34,6 +34,52 @@ pub fn stamp(unix: u64) -> String {
    )
 }

+/// Writes a captured take's loop to `root/takes/` right away, so it survives a reload or a
+/// crash. Never overwrites: a name already taken gets a counter. Returns the file written.
+pub fn save_take(take: &Take, root: &Path, unix: u64) -> std::io::Result<PathBuf> {
+    let folder = root.join("takes");
+    std::fs::create_dir_all(&folder)?;
+    let base = format!(
+        "{}_{:.0}bpm_{}bar{}",
+        stamp(unix),
+        take.tempo(),
+        take.bars,
+        if take.bars == 1 { "" } else { "s" }
+    );
+    let wave = wav::Wave {
+        channels: 2,
+        rate: take.rate.round() as u32,
+        samples: take.audio.clone(),
+        root: None,
+        frame: None,
+    };
+    let bytes = wav::encode(&wave);
+    for n in 1..1000 {
+        let name = if n == 1 {
+            format!("{base}.wav")
+        } else {
+            format!("{base}_{n}.wav")
+        };
+        let path = folder.join(name);
+        match std::fs::OpenOptions::new()
+            .write(true)
+            .create_new(true)
+            .open(&path)
+        {
+            Ok(mut file) => {
+                std::io::Write::write_all(&mut file, &bytes)?;
+                return Ok(path);
+            }
+            Err(e) if e.kind() == std::io::ErrorKind::AlreadyExists => continue,
+            Err(e) => return Err(e),
+        }
+    }
+    Err(std::io::Error::new(
+        std::io::ErrorKind::AlreadyExists,
+        "too many takes with the same name",
+    ))
+}
+
 pub fn export(
    take: &Take,
    settings: &Settings,
@@ -55,7 +101,7 @@ pub fn export(
    let mut files = 1;
    for (i, s) in take.slices.iter().enumerate().filter(|(_, s)| s.enabled) {
        let name = match s.root {
-            Some(n) => format!("s{:02}_{}.wav", i + 1, note_name(n)),
+            Some(n) => format!("s{:02}_{}.wav", i + 1, settings.note_name(n)),
            None => format!("s{:02}.wav", i + 1),
        };
        wav::write(
@@ -5,10 +5,10 @@ mod player;
 mod ring;
 mod settings;
 mod take;
-pub use export::{export, stamp, Exported};
+pub use export::{export, save_take, stamp, Exported};
 pub use player::{Clip, Player, Queues};
 pub use ring::{Marker, Recorder, Ring, Transport, MARKERS};
-pub use settings::{default_folder, Division, Mode, Settings};
+pub use settings::{default_folder, Division, Mode, Settings, SongKey};
 pub use take::{
    capture, render, root_key, transients, wavetable, Segment, Slice, Take, FALLBACK_TEMPO,
    OVERVIEW, TABLE, TABLE_FRAMES,
@@ -48,6 +48,34 @@ impl Division {
    }
 }

+/// The song's key, used to spell slice names.
+#[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq)]
+pub struct SongKey {
+    /// Pitch class of the tonic, 0 = C.
+    pub root: u8,
+    pub minor: bool,
+}
+impl SongKey {
+    /// True for keys written with flats: F, Bb, Eb, Ab, Db, Gb major and D, G, C, F, Bb, Eb
+    /// minor.
+    pub fn flats(self) -> bool {
+        let major = if self.minor {
+            (self.root + 3) % 12
+        } else {
+            self.root % 12
+        };
+        matches!(major, 5 | 10 | 3 | 8 | 1 | 6)
+    }
+    pub fn name(self) -> String {
+        let n = common_dsp::note_name_spelled(self.root % 12 + 12, self.flats());
+        format!(
+            "{} {}",
+            n.trim_end_matches(|c: char| c.is_ascii_digit()),
+            if self.minor { "minor" } else { "major" }
+        )
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
 #[serde(default)]
 pub struct Settings {
@@ -64,8 +92,12 @@ pub struct Settings {
    pub trim: bool,
    /// Also write a wavetable from the selected slice.
    pub wavetable: bool,
+    /// Save every captured take's loop to the `takes` subfolder at once.
+    pub keep_takes: bool,
    /// Export folder; empty selects the default.
    pub folder: String,
+    /// Song key for slice names: flats in flat keys. None spells with sharps.
+    pub key: Option<SongKey>,
 }
 impl Default for Settings {
    fn default() -> Self {
@@ -78,7 +110,9 @@ impl Default for Settings {
            normalize: true,
            trim: true,
            wavetable: false,
+            keep_takes: true,
            folder: String::new(),
+            key: None,
        }
    }
 }
@@ -99,6 +133,13 @@ impl Settings {
        } else {
            2.
        };
+        if let Some(k) = &mut self.key {
+            k.root %= 12;
+        }
+    }
+    /// Name of a slice's note, spelled for the song key.
+    pub fn note_name(&self, note: u8) -> String {
+        common_dsp::note_name_spelled(note, self.key.is_some_and(SongKey::flats))
    }
    pub fn folder(&self) -> PathBuf {
        if !self.folder.trim().is_empty() {
@@ -245,31 +245,35 @@ pub fn transients(x: &[f32], rate: f32, sensitivity: f32) -> Vec<usize> {
    cuts
 }

-/// Root note of a slice, if it is clearly pitched.
+/// Root note of a slice, only when one note is sure over most of it. A growl, a pitch
+/// drop or noise gets no name rather than a wrong one.
 pub fn root_key(yin: &mut Yin, mono: &[f32], rate: f32) -> Option<u8> {
    let window = (2 * yin.max_lag() + 2).min(mono.len());
    if window < (rate / 1000.) as usize * 4 || mono.len() < window {
        return None;
    }
-    // Skip the attack: the body of a hit carries its pitch.
-    let mut notes: Vec<f32> = Vec::new();
+    // Skip the attack: the body of a hit carries its pitch. Spread up to 12 reads over it.
    let start = (mono.len() / 5).min(mono.len() - window);
-    let step = (window / 2).max(1);
-    let mut at = start;
-    while at + window <= mono.len() && notes.len() < 6 {
+    let span = mono.len() - window - start;
+    let count = (span / (window / 2).max(1) + 1).min(12);
+    let mut notes: Vec<f32> = Vec::with_capacity(count);
+    for k in 0..count {
+        let at = start + if count > 1 { span * k / (count - 1) } else { 0 };
        if let Some((hz, clarity)) = yin.estimate(&mono[at..at + window], rate, 35., 1000.) {
            if clarity > 0.7 {
                notes.push(hz_to_midi(hz));
            }
        }
-        at += step;
    }
    if notes.is_empty() {
        return None;
    }
    notes.sort_by(f32::total_cmp);
-    let n = notes[notes.len() / 2].round();
-    (0. ..=127.).contains(&n).then_some(n as u8)
+    let median = notes[notes.len() / 2];
+    let n = median.round();
+    // At least 60 % of all reads, unclear ones included, must sit on that note.
+    let agree = notes.iter().filter(|p| (*p - n).abs() < 0.5).count();
+    (agree * 5 >= count * 3 && (0. ..=127.).contains(&n)).then_some(n as u8)
 }

 /// Builds a take from the newest `bars` complete bars, or from the newest audio when stopped.
@@ -189,6 +189,45 @@ fn root_key_is_detected_per_slice() {
    assert_eq!(silent.slices[0].root, None);
 }

+#[test]
+fn a_slice_whose_pitch_moves_gets_no_note_name() {
+    // Half the slice on F1, half on B1: no one note holds over most of it.
+    let mut a = Saw::new(RATE, 43.65);
+    let mut b = Saw::new(RATE, 61.74);
+    let x: Vec<f32> = (0..48000)
+        .map(|i| 0.5 * if i < 26000 { a.sample() } else { b.sample() })
+        .collect();
+    let take = take_of(x, 120., 1);
+    assert_eq!(take.slices[0].root, None);
+}
+
+#[test]
+fn song_key_spells_slice_names() {
+    let mut s = Settings::default();
+    assert_eq!(s.note_name(39), "D#2");
+    s.key = Some(SongKey {
+        root: 5,
+        minor: true,
+    });
+    assert_eq!(s.note_name(39), "Eb2");
+    assert_eq!(s.key.unwrap().name(), "F minor");
+    s.key = Some(SongKey {
+        root: 4,
+        minor: false,
+    });
+    assert_eq!(s.note_name(39), "D#2");
+    assert!(SongKey {
+        root: 10,
+        minor: false
+    }
+    .flats());
+    assert!(!SongKey {
+        root: 9,
+        minor: true
+    }
+    .flats());
+}
+
 #[test]
 fn wavetable_frames_start_on_rising_zero_crossings_and_match() {
    let mut saw = Saw::new(RATE, 110.);
@@ -231,6 +270,21 @@ fn export_writes_loop_slices_and_wavetable() {
    std::fs::remove_dir_all(&dir).unwrap();
 }

+#[test]
+fn save_take_writes_the_loop_and_never_overwrites() {
+    let dir = std::env::temp_dir().join(format!("crucible-takes-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    let mut saw = Saw::new(RATE, 55.);
+    let take = take_of((0..96000).map(|_| saw.sample() * 0.5).collect(), 120., 1);
+    let first = save_take(&take, &dir, 1_700_000_000).unwrap();
+    let second = save_take(&take, &dir, 1_700_000_000).unwrap();
+    assert!(first.ends_with("takes/2023-11-14_221320_120bpm_1bar.wav"));
+    assert!(second.ends_with("takes/2023-11-14_221320_120bpm_1bar_2.wav"));
+    let w = wav::decode(&std::fs::read(&first).unwrap()).unwrap();
+    assert_eq!(w.samples, take.audio);
+    std::fs::remove_dir_all(&dir).unwrap();
+}
+
 #[test]
 fn audition_plays_and_returns_clips_for_freeing() {
    let q = Queues::default();