feat: stable note tracking, NOTE pitch source and unsure fallback

Producers found the tracked plugins jumpy: the shared tracker switched notes
after 10 ms and retuned every 5 ms, so growls and formant basses flickered
and every tracked plugin acted on wrong notes.

Shared tracker (common-dsp):
- A new note needs a steady read for 40 ms; an octave down 80 ms, an octave
  up 200 ms (an octave-up read still fits the note's period and counts as
  agreeing). Inside a note the tuning only moves past a 0.25 semitone
  deadband. Follow bends keeps the old fast behaviour as an option.
- A trust score turns the note unsure while reads disagree; Tracker::active
  and NoteState report it, and Fallback latches "step back" across note ends.
- Notes end when the window start stays below the gate's release level for
  20 ms, so short gaps between notes are seen without waiting for the gate.
- PitchSource replaces the old (midi, gate, glide) arguments: Audio, MIDI or
  Note mode (a set note, no detection), plus a key lock (minor, major, root
  only) that snaps reads to the key.
- stems.rs: synthetic stems (growls, wobble, reese, formant, 808 slide,
  layered drop, noise riser) and a score; examples/tracker_report scores the
  corpus or real WAV stems. On the corpus the old behaviour makes up to 28
  extra note starts per second; the stable default makes none.

Plugins:
- Anvil, Lathe, Temper, Knurl, Planish, Braze and Forge gain the NOTE pitch
  source, the key lock and Follow bends (shared common-params crate and a
  shared header switch in common-ui).
- Unsure tracking: Anvil brings the original sub back in place of the sine,
  Lathe passes the audio through, Knurl fades its texture out; Temper,
  Planish and Braze hold their last sure tuning. Readouts show the note only
  when it is sure.
- Anvil gains Mode: Replace or Enhance (keeps the original sub and adds the
  sine under it).
- Planish slides its band edges over 6 ms on a new note instead of snapping.
- Ballast defaults to Grid parts, which need no tracking.

plugins/knurl/core/src/lib.rs

@@ -8,7 +8,7 @@
 //! after `new`; mono-safe (both channels get the same treatment).
 mod settings;
 use common_dsp::svf::{Svf, SvfCoef};
-use common_dsp::tracker::{Lookahead, NoteEvent, PitchFollower, Tracked, TrackerConfig};
+use common_dsp::tracker::{Lookahead, NoteEvent, NoteState, PitchFollower, Tracked, TrackerConfig};
 use common_dsp::{coefficient, db_to_gain, hz_to_midi};
 pub use settings::{Seed, Settings, Source, GRIT_OFF, PATTERNS, STEPS, STEP_MIN};
 
@@ -402,8 +402,10 @@ impl Tracked for Module {
         };
         self.pitch.event(self.settings.snap, e);
     }
-    fn process(&mut self, x: [f32; 2], sounding: bool) -> [f32; 2] {
-        self.run(x, sounding)
+    fn process(&mut self, x: [f32; 2], note: NoteState) -> [f32; 2] {
+        // The texture needs a trusted cycle clock: it fades out while tracking is unsure, as
+        // it does between notes.
+        self.run(x, note.sure)
     }
 }
 
@@ -444,7 +446,7 @@ impl Engine {
     fn set_tracker(&mut self, s: &Settings) {
         self.lookahead
             .tracker
-            .set(s.source == Source::Midi, s.gate, false);
+            .set(s.pitch.source(s.source.mode(), s.gate, false));
     }
     pub fn reset(&mut self) {
         self.lookahead.reset();

plugins/knurl/core/src/settings.rs

@@ -1,4 +1,5 @@
 //! Host-independent controls. Gains in dB; amounts relative to one cycle in percent.
+use common_dsp::tracker::{Pitch, PitchMode};
 use serde::{Deserialize, Serialize};
 
 /// Pattern steps: one per cycle, repeating.
@@ -14,6 +15,24 @@ pub enum Source {
     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,
+        }
+    }
 }
 
 #[derive(Debug, Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Default)]
@@ -29,6 +48,9 @@ pub enum Seed {
 #[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,
     /// Gain per pattern step, 0 down to `STEP_MIN`.
     pub pattern: [f32; STEPS],
     /// Steps that get a grit burst.
@@ -104,6 +126,7 @@ impl Default for Settings {
     fn default() -> Self {
         let mut s = Self {
             source: Source::Audio,
+            pitch: Pitch::default(),
             pattern: [0.; STEPS],
             grit_steps: [true; STEPS],
             steps: 1,
@@ -127,6 +150,7 @@ impl Default for Settings {
 }
 impl Settings {
     pub fn validate(&self) -> Result<(), &'static str> {
+        self.pitch.validate()?;
         let finite = [
             self.edge,
             self.level_jitter,

plugins/knurl/plugin/Cargo.lock

@@ -309,11 +309,23 @@ 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",
 ]
 
@@ -864,6 +876,7 @@ name = "knurl"
 version = "0.2.0"
 dependencies = [
  "clap-sys",
+ "common-params",
  "crossbeam-queue",
  "knurl-core",
  "knurl-ui",

plugins/knurl/plugin/Cargo.toml

@@ -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" }
 knurl-core = { path = "../core" }
+common-params = { path = "../../common/params" }
 knurl-ui = { path = "../ui" }
 crossbeam-queue = "0.3"
 serde = { version = "1", features = ["derive"] }

plugins/knurl/plugin/src/params.rs

@@ -1,3 +1,4 @@
+use common_params::PitchParams;
 use knurl_core::{Seed, Settings, Source, GRIT_OFF, STEPS, STEP_MIN};
 use nih_plug::prelude::*;
 use nih_plug_egui::EguiState;
@@ -10,6 +11,26 @@ 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 SeedParam {
@@ -50,6 +71,8 @@ pub struct KnurlParams {
     pub pattern: RwLock<Pattern>,
     #[id = "source"]
     pub source: EnumParam<SourceParam>,
+    #[nested(group = "Pitch")]
+    pub pitch: PitchParams,
     #[id = "seed"]
     pub seed: EnumParam<SeedParam>,
     #[id = "steps"]
@@ -86,6 +109,7 @@ impl Default for KnurlParams {
             editor: EguiState::from_size(knurl_ui::WIDTH, knurl_ui::HEIGHT),
             pattern: RwLock::new(Pattern::default()),
             source: EnumParam::new("Pitch source", SourceParam::Audio),
+            pitch: PitchParams::default(),
             seed: EnumParam::new("Random", SeedParam::Same),
             steps: IntParam::new(
                 "Steps",
@@ -131,10 +155,8 @@ impl KnurlParams {
     pub fn settings(&self, last: &Pattern) -> Settings {
         let pattern = self.pattern.try_read().map(|p| *p).unwrap_or(*last);
         Settings {
-            source: match self.source.value() {
-                SourceParam::Audio => Source::Audio,
-                SourceParam::Midi => Source::Midi,
-            },
+            source: self.source.value().into(),
+            pitch: self.pitch.pitch(),
             pattern: pattern.gains.map(|g| {
                 if g.is_finite() {
                     g.clamp(STEP_MIN, 0.)
@@ -238,12 +260,9 @@ impl KnurlParams {
             switch(setter, &self.bypass, new.bypass);
         }
         if new.source != old.source {
-            let v = match new.source {
-                Source::Audio => SourceParam::Audio,
-                Source::Midi => SourceParam::Midi,
-            };
-            switch(setter, &self.source, v);
+            switch(setter, &self.source, new.source.into());
         }
+        self.pitch.apply(setter, &old.pitch, &new.pitch);
         if new.seed != old.seed {
             let v = match new.seed {
                 Seed::Same => SeedParam::Same,

plugins/knurl/ui/src/lib.rs

@@ -78,13 +78,9 @@ pub fn show(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
             settings.bypass = !settings.bypass;
         }
         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;
-            }
-        }
-        caption(ui, "PITCH FROM");
+        let mut mode = settings.source.mode();
+        pitch_from(ui, &mut mode, &mut settings.pitch);
+        settings.source = Source::from_mode(mode);
     });
     body(ui, settings, state);
     ui.separator();