Replace the 5-Band-EQ with the Parametric EQ and remove it (#395)

The Parametric EQ does all the 5-Band-EQ did and more, so the editor
keeps only one EQ. The old node was used in one project only, with
nothing linked to its band inputs.

- "Garden of Sacrifices" was converted once on the project file, not
  by a load migration (#137). Its 5 nodes are Parametric EQs now with
  the same filters: low shelf 80 Hz, peaks at 250 Hz, 1 kHz and 4 kHz
  with Q 1, high shelf 12 kHz. A band at 0 became no band.
- Two values below -24 dB were held to -24, as the Parametric EQ goes
  no further. Both are in the asset "Delay" (high -60, low -36). The
  user will rework them by ear.
- The write went through the API's own Store (lock, revision 20181 to
  20182), so a tab with the old revision gets a 409 instead of
  overwriting it.
- Removed with the node: its stage kind "filter" and the type
  FxFilter, which nothing else made, and the player's branch for it.
  A Pan is now the last branch of fxNodes, a Flanger that of stagesOf.
- Tests that took the 5-Band-EQ as "some effect" use the Pan or the
  Parametric EQ now. The test for a parameter feeding a band now
  feeds the cutoff of a Filter, which had no such test yet.
- A project that still names the type, such as an old snapshot of
  "Garden of Sacrifices", loads without those nodes. Unknown types
  were always left out on load.

Tests:
- Unit (stein2): soundfx 67, instrument 36, envelope 13, sound-library
  127, all green
- Counter-check: with the cutoff not taken from the parameter, only
  the new Filter test goes red
- The converted project loads and compiles: Delay, Vocals and Drums
  play their bands (3+1, 4 and 5)
- e2e 34 (atx): ALL PASSED, 136 checks, the palette check now looks
  for the Parametric EQ
- Gate (atx): CHECK EXIT 0, 288 files, 4417 tests

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/core/soundfx/nodes.ts

@@ -20,21 +20,17 @@ import { eqBandsOf, eqStagesOf, hasGain, isEqBandHeard, MAX_EQ_BANDS, type PassB
 
 export { SOUND_FX_INPUT, SOUND_FX_OUTPUT };
 
-/** The filter shapes the EQ uses – Web Audio's names, so the player hands them on as they are. */
-export type FxFilter = 'lowshelf' | 'peaking' | 'highshelf';
-
 /** The shapes of a Filter (#335, #318), Web Audio's names. */
 export type FxPassFilter =
   'lowpass' | 'highpass' | 'bandpass' | 'notch' | 'lowshelf' | 'highshelf' | 'peaking' | 'allpass';
 
 /**
- * One step a voice passes on its way out: a volume, one band of an equalizer, a filter, the volume an
+ * One step a voice passes on its way out: a volume, a filter or a band of an EQ, the volume an
  * Envelope gives a note (#335), or an echo (#327). An echo's `damping` is already the cutoff of the
  * low-pass in its feedback, in Hz. A `mod` is an Envelope moving that number while the note plays.
  */
 export type FxStage =
   | { kind: 'gain'; gain: number; mod?: FxMod }
-  | { kind: 'filter'; filter: FxFilter; frequency: number; gain: number; q: number; mod?: FxMod }
   | FxPass
   | { kind: 'envelope'; envelope: FxEnvelope }
   | FxDelay
@@ -298,7 +294,6 @@ export interface FxAmount {
 
 export type FxStagePlan =
   | { kind: 'gain'; db: FxAmount }
-  | { kind: 'filter'; filter: FxFilter; frequency: number; gain: FxAmount; q: number }
   | { kind: 'pass'; filter: FxPassFilter; stages: number; cutoff: FxAmount; q: FxAmount; gain: FxAmount }
   | { kind: 'envelope'; envelope: FxEnvelopePlan }
   | {
@@ -588,43 +583,6 @@ export const SoundFxPitch: SoundFxNodeDef = effect(
   'own',
 );
 
-/** The five bands of the EQ: a shelf at either end and three peaks between them. */
-const EQ_BANDS: readonly { key: string; label: string; filter: FxFilter; frequency: number }[] = [
-  { key: 'low', label: '80 Hz', filter: 'lowshelf', frequency: 80 },
-  { key: 'lowMid', label: '250 Hz', filter: 'peaking', frequency: 250 },
-  { key: 'mid', label: '1 kHz', filter: 'peaking', frequency: 1000 },
-  { key: 'highMid', label: '4 kHz', filter: 'peaking', frequency: 4000 },
-  { key: 'high', label: '12 kHz', filter: 'highshelf', frequency: 12000 },
-];
-
-/** About an octave and a half wide: neighbouring peaks overlap, so no frequency falls between them. */
-const PEAK_Q = 1;
-const EQ_ROWS = EQ_BANDS.map((band) => numberRow(band.key, band.label, -60, 24, 0.5));
-
-export const SoundFxEq: SoundFxNodeDef = effect(
-  {
-    type: 'SoundFxEq',
-    label: '5-Band-EQ',
-    category: 'sound',
-    description:
-      'A five-band equalizer: raises or lowers the lows (80 Hz), low mids (250 Hz), mids (1 kHz), high mids (4 kHz) and highs (12 kHz), each in decibels. A band at 0 does nothing.' +
-      BLENDS,
-    inputs: [audioIn, ...EQ_ROWS.map(followingIn)],
-    outputs: [audioOut],
-    params: [],
-    emit: (sounds, amounts) => {
-      const stages: FxStagePlan[] = [];
-      EQ_BANDS.forEach((band, i) => {
-        const gain = held(amounts[band.key], EQ_ROWS[i]!);
-        if (!isNone(gain))
-          stages.push({ kind: 'filter', filter: band.filter, frequency: band.frequency, gain, q: PEAK_Q });
-      });
-      return withStages(arriving(sounds), stages);
-    },
-  },
-  'blend',
-);
-
 export const SoundFxParametricEq: SoundFxNodeDef = effect(
   {
     type: 'SoundFxParametricEq',
@@ -1326,7 +1284,6 @@ export const SOUND_FX_NODES: readonly SoundFxNodeDef[] = [
   SoundFxOutput,
   SoundFxGain,
   SoundFxPitch,
-  SoundFxEq,
   SoundFxParametricEq,
   SoundFxFilter,
   SoundFxMix,
@@ -1542,26 +1499,19 @@ function stagesOf(plan: readonly FxStagePlan[], params: FxParams, tempo: number)
         stages.push({ kind: 'pan', pan, ...(mod && { mod }) });
       continue;
     }
-    if (stage.kind === 'flanger') {
-      const offsetMod = modOf(stage.offset, params);
-      const mixMod = modOf(stage.mix, params);
-      stages.push({
-        kind: 'flanger',
-        offset: amountOf(stage.offset, params),
-        sweep: amountOf(stage.sweep, params),
-        rate: amountOf(stage.rate, params),
-        depth: amountOf(stage.depth, params),
-        feedback: amountOf(stage.feedback, params),
-        mix: amountOf(stage.mix, params),
-        ...(offsetMod && { offsetMod }),
-        ...(mixMod && { mixMod }),
-      });
-      continue;
-    }
-    const gain = amountOf(stage.gain, params);
-    const mod = modOf(stage.gain, params);
-    if (gain !== 0 || stage.gain.param !== undefined || mod)
-      stages.push({ ...stage, gain, ...(mod && { mod }) });
+    const offsetMod = modOf(stage.offset, params);
+    const mixMod = modOf(stage.mix, params);
+    stages.push({
+      kind: 'flanger',
+      offset: amountOf(stage.offset, params),
+      sweep: amountOf(stage.sweep, params),
+      rate: amountOf(stage.rate, params),
+      depth: amountOf(stage.depth, params),
+      feedback: amountOf(stage.feedback, params),
+      mix: amountOf(stage.mix, params),
+      ...(offsetMod && { offsetMod }),
+      ...(mixMod && { mixMod }),
+    });
   }
   return stages;
 }

src/viewport/fxNodes.ts

@@ -133,26 +133,13 @@ export function stageNodes(
       { name: 'release', value: stage.release, even: 'ratio' },
       { name: 'autoGain', value: stage.autoGain, even: 'value' },
     ]);
-  if (stage.kind === 'pan') {
-    const panner = context.createStereoPanner();
-    panner.pan.value = stage.mod ? 0 : stage.pan;
-    if (stage.mod) follow?.(stage.mod, panner.pan, false);
-    return {
-      input: panner,
-      output: panner,
-      knobs: [{ param: stage.mod ? null : panner.pan, target: stage.pan, even: 'value' }],
-    };
-  }
-  const filter = context.createBiquadFilter();
-  filter.type = stage.filter;
-  filter.frequency.value = stage.frequency;
-  filter.gain.value = stage.mod ? 0 : stage.gain;
-  filter.Q.value = stage.q;
-  if (stage.mod) follow?.(stage.mod, filter.gain, false);
+  const panner = context.createStereoPanner();
+  panner.pan.value = stage.mod ? 0 : stage.pan;
+  if (stage.mod) follow?.(stage.mod, panner.pan, false);
   return {
-    input: filter,
-    output: filter,
-    knobs: [{ param: stage.mod ? null : filter.gain, target: stage.gain, even: 'value' }],
+    input: panner,
+    output: panner,
+    knobs: [{ param: stage.mod ? null : panner.pan, target: stage.pan, even: 'value' }],
   };
 }