fix modulation wheel multiplier implementation

spessasus · spessasus · commit 00a2fe8debef · 2026-04-04T03:20:07.000+02:00
diff --git a/src/soundbank/basic_soundbank/modulator.ts b/src/soundbank/basic_soundbank/modulator.ts
@@ -73,13 +73,18 @@ export class Modulator {
      * - still can be disabled if the soundfont has its own modulator curve
      * - this fixes the very low amount of reverb by default and doesn't break soundfonts
      */
-    public readonly isEffectModulator: boolean = false;
+    public readonly isEffectModulator;
 
     /**
      * The default resonant modulator does not affect the filter gain.
      * Neither XG nor GS responded to cc #74 in that way.
      */
-    public readonly isDefaultResonantModulator: boolean = false;
+    public readonly isDefaultResonantModulator;
+
+    /**
+     * If this is a modulation wheel modulator (for modulation depth range).
+     */
+    public readonly isModWheelModulator;
 
     /**
      * The primary source of this modulator.
@@ -101,7 +106,8 @@ export class Modulator {
         amount = 0,
         transformType: ModulatorTransformType = 0,
         isEffectModulator = false,
-        isDefaultResonantModulator = false
+        isDefaultResonantModulator = false,
+        isModWheelModulator = false
     ) {
         this.primarySource = primarySource;
         this.secondarySource = secondarySource;
@@ -111,6 +117,7 @@ export class Modulator {
         this.transformType = transformType;
         this.isEffectModulator = isEffectModulator;
         this.isDefaultResonantModulator = isDefaultResonantModulator;
+        this.isModWheelModulator = isModWheelModulator;
     }
 
     private get destinationName() {
@@ -155,7 +162,8 @@ export class Modulator {
             mod.transformAmount,
             mod.transformType,
             mod.isEffectModulator,
-            mod.isDefaultResonantModulator
+            mod.isDefaultResonantModulator,
+            mod.isModWheelModulator
         );
     }
 
@@ -220,14 +228,22 @@ export class DecodedModulator extends Modulator {
             secondarySourceEnum === 0x0 &&
             destination === generatorTypes.initialFilterQ;
 
+        const s1 = ModulatorSource.fromSourceEnum(sourceEnum);
+        const s2 = ModulatorSource.fromSourceEnum(secondarySourceEnum);
+
+        const isModWheelModulator =
+            (s1.isCC && s1.index === midiControllers.modulationWheel) ||
+            (s2.isCC && s2.index === midiControllers.modulationWheel);
+
         super(
-            ModulatorSource.fromSourceEnum(sourceEnum),
-            ModulatorSource.fromSourceEnum(secondarySourceEnum),
+            s1,
+            s2,
             destination,
             amount,
             transformType as ModulatorTransformType,
             isEffectModulator,
-            isDefaultResonantModulator
+            isDefaultResonantModulator,
+            isModWheelModulator
         );
 
         if (this.destination > MAX_GENERATOR) {
diff --git a/src/soundbank/basic_soundbank/modulator_source.ts b/src/soundbank/basic_soundbank/modulator_source.ts
@@ -199,7 +199,7 @@ export class ModulatorSource {
         const transformType =
             (this.isBipolar ? 0b10 : 0b00) | (this.isNegative ? 1 : 0);
 
-        return precomputedTransforms[
+        return precomputedModulatorTransforms[
             MODULATOR_RESOLUTION *
                 (this.curveType * MOD_CURVE_TYPES_AMOUNT + transformType) +
                 rawValue
@@ -211,7 +211,7 @@ export class ModulatorSource {
  * To get the value, you do
  * MODULATOR_RESOLUTION * (MOD_CURVE_TYPES_AMOUNT * curveType + transformType) + your raw value as 14-bit number (0 - 16,383)
  */
-const precomputedTransforms = new Float32Array(
+export const precomputedModulatorTransforms = new Float32Array(
     MODULATOR_RESOLUTION *
         MOD_SOURCE_TRANSFORM_POSSIBILITIES *
         MOD_CURVE_TYPES_AMOUNT
@@ -227,11 +227,12 @@ for (let curveType = 0; curveType < MOD_CURVE_TYPES_AMOUNT; curveType++) {
             MODULATOR_RESOLUTION *
             (curveType * MOD_CURVE_TYPES_AMOUNT + transformType);
         for (let value = 0; value < MODULATOR_RESOLUTION; value++) {
-            precomputedTransforms[tableIndex + value] = getModulatorCurveValue(
-                transformType,
-                curveType as ModulatorCurveType,
-                value / MODULATOR_RESOLUTION
-            );
+            precomputedModulatorTransforms[tableIndex + value] =
+                getModulatorCurveValue(
+                    transformType,
+                    curveType as ModulatorCurveType,
+                    value / MODULATOR_RESOLUTION
+                );
         }
     }
 }
diff --git a/src/synthesizer/audio_engine/engine_components/compute_modulator.ts b/src/synthesizer/audio_engine/engine_components/compute_modulator.ts
@@ -2,15 +2,74 @@ import { generatorLimits } from "../../../soundbank/basic_soundbank/generator_ty
 import type { MIDIChannel } from "./midi_channel";
 import type { Voice } from "./voice";
 import { modulatorSources } from "../../../soundbank/enums";
-import { NON_CC_INDEX_OFFSET } from "./controller_tables"; /**
+import { NON_CC_INDEX_OFFSET } from "./controller_tables";
+import { customControllers } from "../../enums";
+
+/**
  * Compute_modulator.ts
  * purpose: contains a function for computing all modulators
  */
+const EFFECT_MODULATOR_TRANSFORM_MULTIPLIER = 1000 / 200;
 
 /**
- * Compute_modulator.ts
- * purpose: contains a function for computing all modulators
+ * Computes a given modulator
+ * @param voice the voice of this modulator.
+ * @param pitchWheel the pitch wheel value, as channel determines if it's a per-note or a global value.
+ * @param modulatorIndex the modulator to compute
+ * @returns the computed value
  */
+export function computeModulator(
+    this: MIDIChannel,
+    voice: Voice,
+    pitchWheel: number,
+    modulatorIndex: number
+) {
+    const modulator = voice.modulators[modulatorIndex];
+    if (modulator.transformAmount === 0) {
+        voice.modulatorValues[modulatorIndex] = 0;
+        return 0;
+    }
+    const sourceValue = modulator.primarySource.getValue(
+        this.midiControllers,
+        pitchWheel,
+        voice
+    );
+    const secondSrcValue = modulator.secondarySource.getValue(
+        this.midiControllers,
+        pitchWheel,
+        voice
+    );
+
+    // See the comment for isEffectModulator (modulator.ts in basic_soundbank) for explanation
+    let transformAmount = modulator.transformAmount;
+    if (modulator.isEffectModulator && transformAmount <= 1000) {
+        transformAmount *= EFFECT_MODULATOR_TRANSFORM_MULTIPLIER;
+        transformAmount = Math.min(transformAmount, 1000);
+    }
+
+    // Compute the modulator
+    let computedValue = sourceValue * secondSrcValue * transformAmount;
+
+    if (modulator.transformType === 2) {
+        // Abs value
+        computedValue = Math.abs(computedValue);
+    }
+
+    // Resonant modulator: take its value and ensure that it won't change the final gain
+    if (modulator.isDefaultResonantModulator) {
+        // Half the gain, negates the filter
+        voice.resonanceOffset = Math.max(0, computedValue / 2);
+    }
+
+    // Modulation depth
+    if (modulator.isModWheelModulator) {
+        computedValue *=
+            this.customControllers[customControllers.modulationMultiplier];
+    }
+
+    voice.modulatorValues[modulatorIndex] = computedValue;
+    return computedValue;
+}
 
 /**
  * Computes modulators of a given voice. Source and index indicate what modulators shall be computed.
@@ -53,7 +112,7 @@ export function computeModulators(
                 Math.max(
                     -32_768,
                     modulatedGenerators[mod.destination] +
-                        voice.computeModulator(this.midiControllers, pitch, i)
+                        this.computeModulator(voice, pitch, i)
                 )
             );
         }
@@ -87,7 +146,7 @@ export function computeModulators(
             const destination = mod.destination;
             let outputValue = generators[destination];
             // Compute our modulator
-            voice.computeModulator(this.midiControllers, pitch, i);
+            this.computeModulator(voice, pitch, i);
 
             // Sum the values of all modulators for this destination
             for (let j = 0; j < modulators.length; j++) {
diff --git a/src/synthesizer/audio_engine/engine_components/dsp_chain/render_voice.ts b/src/synthesizer/audio_engine/engine_components/dsp_chain/render_voice.ts
@@ -3,7 +3,6 @@ import { getLFOValueSine } from "./lfo";
 import type { Voice } from "../voice";
 import type { MIDIChannel } from "../midi_channel";
 import { generatorTypes } from "../../../../soundbank/basic_soundbank/generator_types";
-import { customControllers } from "../../../enums";
 import { midiControllers } from "../../../../midi/enums";
 import { LowpassFilter } from "./lowpass_filter";
 
@@ -126,13 +125,7 @@ export function renderVoice(
             const rateInc = (vibFreqHz * sampleCount) / sampleRate;
             const vibLfoValue = 1 - 4 * Math.abs(voice.vibLfoPhase - 0.5);
             if ((voice.vibLfoPhase += rateInc) >= 1) voice.vibLfoPhase -= 1;
-            // Use modulation multiplier (RPN modulation depth)
-            cents +=
-                vibLfoValue *
-                (vibPitchDepth *
-                    this.customControllers[
-                        customControllers.modulationMultiplier
-                    ]);
+            cents += vibLfoValue * vibPitchDepth;
             // Low pass frequency
             lowpassExcursion += vibLfoValue * vibFilterDepth;
 
@@ -164,13 +157,7 @@ export function renderVoice(
             const rateInc = (modFreqHz * sampleCount) / sampleRate;
             const modLfoValue = 1 - 4 * Math.abs(voice.modLfoPhase - 0.5);
             if ((voice.modLfoPhase += rateInc) >= 1) voice.modLfoPhase -= 1;
-            // Use modulation multiplier (RPN modulation depth)
-            cents +=
-                modLfoValue *
-                (modPitchDepth *
-                    this.customControllers[
-                        customControllers.modulationMultiplier
-                    ]);
+            cents += modLfoValue * modPitchDepth;
             // Vol env volume offset
             // Negate the lfo value because audigy starts with increase rather than decrease
             volumeExcursionCentibels += -modLfoValue * modVolDepth;
diff --git a/src/synthesizer/audio_engine/engine_components/midi_channel.ts b/src/synthesizer/audio_engine/engine_components/midi_channel.ts
@@ -22,7 +22,7 @@ import {
     GENERATOR_OVERRIDE_NO_CHANGE_VALUE
 } from "./synth_constants";
 import { DynamicModulatorSystem } from "./dynamic_modulator_system";
-import { computeModulators } from "./compute_modulator";
+import { computeModulator, computeModulators } from "./compute_modulator";
 import {
     generatorLimits,
     GENERATORS_AMOUNT,
@@ -288,6 +288,7 @@ export class MIDIChannel {
      * A small optimization that disables applying overrides until at least one is set.
      */
     protected generatorOverridesEnabled = false;
+    protected readonly computeModulator = computeModulator.bind(this);
     protected readonly computeModulators = computeModulators.bind(this);
     /**
      * For tracking voice count changes
diff --git a/src/synthesizer/audio_engine/engine_components/voice.ts b/src/synthesizer/audio_engine/engine_components/voice.ts
@@ -19,7 +19,6 @@ import { type InterpolationType } from "../../enums";
 import { DEFAULT_MASTER_PARAMETERS } from "./master_parameters";
 
 const EXCLUSIVE_CUTOFF_TIME = -2320;
-const EFFECT_MODULATOR_TRANSFORM_MULTIPLIER = 1000 / 200;
 
 /**
  * Voice represents a single instance of the
@@ -255,60 +254,6 @@ export class Voice {
         this.filter = new LowpassFilter(sampleRate);
     }
 
-    /**
-     * Computes a given modulator
-     * @param controllerTable all midi controllers as 14bit values + the non-controller indexes, starting at 128
-     * @param pitchWheel the pitch wheel value, as channel determines if it's a per-note or a global value.
-     * @param modulatorIndex the modulator to compute
-     * @returns the computed value
-     */
-    public computeModulator(
-        this: Voice,
-        controllerTable: Int16Array,
-        pitchWheel: number,
-        modulatorIndex: number
-    ): number {
-        const modulator = this.modulators[modulatorIndex];
-        if (modulator.transformAmount === 0) {
-            this.modulatorValues[modulatorIndex] = 0;
-            return 0;
-        }
-        const sourceValue = modulator.primarySource.getValue(
-            controllerTable,
-            pitchWheel,
-            this
-        );
-        const secondSrcValue = modulator.secondarySource.getValue(
-            controllerTable,
-            pitchWheel,
-            this
-        );
-
-        // See the comment for isEffectModulator (modulator.ts in basic_soundbank) for explanation
-        let transformAmount = modulator.transformAmount;
-        if (modulator.isEffectModulator && transformAmount <= 1000) {
-            transformAmount *= EFFECT_MODULATOR_TRANSFORM_MULTIPLIER;
-            transformAmount = Math.min(transformAmount, 1000);
-        }
-
-        // Compute the modulator
-        let computedValue = sourceValue * secondSrcValue * transformAmount;
-
-        if (modulator.transformType === 2) {
-            // Abs value
-            computedValue = Math.abs(computedValue);
-        }
-
-        // Resonant modulator: take its value and ensure that it won't change the final gain
-        if (modulator.isDefaultResonantModulator) {
-            // Half the gain, negates the filter
-            this.resonanceOffset = Math.max(0, computedValue / 2);
-        }
-
-        this.modulatorValues[modulatorIndex] = computedValue;
-        return computedValue;
-    }
-
     /**
      * Releases the voice as exclusiveClass.
      */
