docs(ideas): record producer feedback on note tracking and usability

Producers find most plugins confusing: the note readout flickers on real
basses, and Anvil did not do what they expected. Record the causes (one
shared fast-reacting tracker behind nine plugins, wrong guesses acted on,
DSP-named controls, hidden MIDI routing), principles for the next round and
an order of work.

docs/ideas.md

@@ -91,6 +91,125 @@ Patina. Findings from the audit:
 - **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.
+
 ## Research findings (2026-11)
 
 From the papers in `research/` (local, not committed). Each finding names where