Procedural Analog Drum Synthesis Overhaul

src/logic/DrumMachine.ts

@@ -99,6 +99,17 @@ export class DrumMachine {
         this.params[drum] = { pitch, decay }
     }
 
+    /**
+     * Synchronizes all internal parameters from the store's state.
+     */
+    syncInternalParams(kit: '808' | '909', drive: number, drumParams: any) {
+        this.setKit(kit);
+        this.setSaturation(drive);
+        for (const drumId in drumParams) {
+            this.setDrumParams(drumId, drumParams[drumId].pitch, drumParams[drumId].decay);
+        }
+    }
+
     triggerDrum(drum: 'kick' | 'snare' | 'hihat' | 'hihatOpen' | 'clap' | 'cowbell', time: number, velocity: number = 0.8) {
         const p = this.params[drum]
         const kit808 = this.kit808

src/logic/DrumUtils.ts

@@ -1,3 +1,5 @@
+import * as Tone from 'tone'
+
 /**
  * Shared DSP utilities for drum synthesis based on research specs.
  */
@@ -21,13 +23,14 @@ export function makeDistortionCurve(amount: number = 20): Float32Array {
 }
 
 /**
- * Applies micro-randomization to a base frequency (Pitch Drift).
- * Typically +/- 1Hz as per research.
+ * Applies micro-randomization to a base frequency (Pitch Drift) using cents.
+ * Formula: f_new = f_base * Math.pow(2, cents / 1200)
  * @param base - Base frequency in Hz
- * @param range - Drift range in Hz (default 1.0)
+ * @param centsRange - Drift range in cents (default 1.0)
  */
-export function applyPitchDrift(base: number, range: number = 1.0): number {
-    return base + (Math.random() * 2 - 1) * range;
+export function applyPitchDrift(base: number, centsRange: number = 1.0): number {
+    const drift = (Math.random() * 2 - 1) * centsRange;
+    return base * Math.pow(2, drift / 1200);
 }
 
 /**
@@ -37,6 +40,40 @@ export function applyPitchDrift(base: number, range: number = 1.0): number {
  * @param variance - Variance percentage (e.g. 0.02 for 2%)
  */
 export function applyVariance(base: number, variance: number = 0.02): number {
-    // Math.random() * 0.04 - 0.02 gives range [-0.02, 0.02]
+    // Math.random() * (variance * 2) - variance gives range [-variance, variance]
     return base * (1 + (Math.random() * (variance * 2) - variance));
 }
+
+/**
+ * Generates a 2-second buffer of white noise.
+ * @param context - Audio context
+ */
+export function generateWhiteNoise(context: Tone.BaseContext): AudioBuffer {
+    const bufferSize = context.sampleRate * 2.0;
+    const buffer = context.createBuffer(1, bufferSize, context.sampleRate);
+    const data = buffer.getChannelData(0);
+    for (let i = 0; i < bufferSize; i++) {
+        data[i] = Math.random() * 2 - 1;
+    }
+    return buffer;
+}
+
+/**
+ * Generates a 2-second buffer of 15-bit LFSR (Linear Feedback Shift Register) noise.
+ * This provides an authentic "digital" texture for TR-909 snappy components.
+ * @param context - Audio context
+ */
+export function generateLFSRNoise(context: Tone.BaseContext): AudioBuffer {
+    const bufferSize = context.sampleRate * 2.0;
+    const buffer = context.createBuffer(1, bufferSize, context.sampleRate);
+    const data = buffer.getChannelData(0);
+    let lfsr = 0x7FFF; // 15-bit register, non-zero start
+
+    for (let i = 0; i < bufferSize; i++) {
+        // 15-bit LFSR with taps at bits 14 and 15 (x^15 + x^14 + 1)
+        const bit = ((lfsr >> 0) ^ (lfsr >> 1)) & 1;
+        lfsr = (lfsr >> 1) | (bit << 14);
+        data[i] = ((lfsr & 1) * 2 - 1) * 0.5; // Scaled to [-0.5, 0.5] for texture
+    }
+    return buffer;
+}

src/logic/drums/TR808Clap.ts

@@ -1,17 +1,16 @@
 import * as Tone from 'tone'
-import { applyVariance } from '../DrumUtils'
+import { applyVariance, generateWhiteNoise } from '../DrumUtils'
 
 export class TR808Clap {
     private noiseBuffer: AudioBuffer;
 
     constructor(private destination: Tone.ToneAudioNode) {
-        const sampleRate = Tone.getContext().sampleRate;
-        this.noiseBuffer = Tone.getContext().createBuffer(1, sampleRate * 0.5, sampleRate);
-        const data = this.noiseBuffer.getChannelData(0);
-        for (let i = 0; i < data.length; i++) data[i] = Math.random() * 2 - 1;
+        this.noiseBuffer = generateWhiteNoise(Tone.getContext());
     }
 
     trigger(time: number, pitch: number, decay: number, velocity: number = 0.8) {
+        if (velocity <= 0) return;
+
         const noiseSrc = new Tone.BufferSource(this.noiseBuffer);
         const bpfFreq = (1000 + pitch * 1000);
         const bpf = new Tone.Filter(applyVariance(bpfFreq, 0.02), "bandpass");
@@ -25,21 +24,24 @@ export class TR808Clap {
         const snapIntervalBase = 0.01;
         const snapInterval = applyVariance(snapIntervalBase, 0.02);
 
+        const v = Math.max(0.001, velocity);
         for (let i = 0; i < snapCount; i++) {
             const snapTime = time + i * snapInterval;
-            gain.gain.setValueAtTime(velocity, snapTime);
-            gain.gain.exponentialRampToValueAtTime(velocity * 0.1, snapTime + snapInterval * 0.8);
+            gain.gain.setValueAtTime(v, snapTime);
+            gain.gain.exponentialRampToValueAtTime(Math.max(0.001, v * 0.1), snapTime + snapInterval * 0.8);
         }
 
         // Final decay
         const finalDecayStart = time + snapCount * snapInterval;
         const decayTimeBase = 0.1 + decay * 0.5;
         const decayTime = applyVariance(decayTimeBase, 0.02);
 
-        gain.gain.setValueAtTime(velocity, finalDecayStart);
+        gain.gain.setValueAtTime(v, finalDecayStart);
         gain.gain.exponentialRampToValueAtTime(0.001, finalDecayStart + decayTime);
 
-        noiseSrc.start(time).stop(finalDecayStart + decayTime);
+        // Random start offset to avoid machine-gun effect
+        const randomStart = Math.random() * (this.noiseBuffer.duration - (finalDecayStart - time) - decayTime - 0.1);
+        noiseSrc.start(time, randomStart).stop(finalDecayStart + decayTime);
 
         noiseSrc.onended = () => {
             noiseSrc.dispose();

src/logic/drums/TR808Cowbell.ts

@@ -7,6 +7,8 @@ export class TR808Cowbell {
     constructor(private destination: Tone.ToneAudioNode) { }
 
     trigger(time: number, pitch: number, decay: number, velocity: number = 0.8) {
+        if (velocity <= 0) return;
+
         // Core: Dual square wave oscillators from Schmitt trigger matrix
         // Standard frequencies: 540Hz and 800Hz
         const pitchMultiplier = 0.5 + pitch; // Range approx 0.5x to 1.5x
@@ -30,7 +32,8 @@ export class TR808Cowbell {
 
         const decayTime = applyVariance(0.1 + decay * 0.4, 0.02);
 
-        vca.gain.setValueAtTime(velocity, time);
+        const v = Math.max(0.001, velocity);
+        vca.gain.setValueAtTime(v, time);
         vca.gain.exponentialRampToValueAtTime(0.001, time + decayTime);
 
         this.activeGains.add(vca);

src/logic/drums/TR808HiHat.ts

@@ -8,6 +8,8 @@ export class TR808HiHat {
     constructor(private destination: Tone.ToneAudioNode) { }
 
     trigger(time: number, isOpen: boolean, pitch: number, decay: number, velocity: number = 0.8) {
+        if (velocity <= 0) return;
+
         // Create nodes
         const mixGain = new Tone.Gain(0.15);
         const bpf1 = new Tone.Filter(3440, "bandpass");
@@ -20,15 +22,14 @@ export class TR808HiHat {
 
         // Create 6 Square Wave Oscillators (Schmitt Trigger Matrix)
         const oscillators = this.frequencies.map(freq => {
-            const driftedFreq = applyPitchDrift(freq * pitchMultiplier, 2.0); // +/- 2Hz drift for hats
+            const driftedFreq = applyPitchDrift(freq * pitchMultiplier, 2.0); // 2 cents drift
             const osc = new Tone.Oscillator(driftedFreq, "square");
             osc.phase = Math.random() * 360;
             osc.connect(mixGain);
             return osc;
         });
 
         // Routing Graph
-        // Oscillators -> MixGain -> [BPF1, BPF2] (Parallel) -> EnvGain -> HPF -> Destination
         mixGain.connect(bpf1);
         mixGain.connect(bpf2);
         bpf1.connect(envGain);
@@ -48,7 +49,8 @@ export class TR808HiHat {
         const decayTime = applyVariance(decayBase, 0.02);
 
         // VCA Envelope
-        envGain.gain.setValueAtTime(velocity, time);
+        const v = Math.max(0.001, velocity);
+        envGain.gain.setValueAtTime(v, time);
         envGain.gain.exponentialRampToValueAtTime(0.001, time + decayTime);
 
         this.activeGains.add(envGain);
@@ -58,8 +60,7 @@ export class TR808HiHat {
             osc.start(time).stop(time + decayTime);
         });
 
-        // Disposal - Explicitly clean up all 11-12 nodes to prevent memory leaks
-        // We use the first oscillator's onstop event to trigger the cleanup
+        // Disposal
         oscillators[0].onstop = () => {
             oscillators.forEach(o => o.dispose());
             mixGain.dispose();

src/logic/drums/TR808Kick.ts

@@ -5,6 +5,8 @@ export class TR808Kick {
     constructor(private destination: Tone.ToneAudioNode) { }
 
     trigger(time: number, pitch: number, decay: number, velocity: number = 0.8) {
+        if (velocity <= 0) return;
+
         // pitch: 0.5 -> 52.5Hz, maps to 45-60Hz range
         const tune = 45 + pitch * 15;
         // decay: 0.5 -> 1.7s, maps to 0.4-3.0s range
@@ -19,22 +21,30 @@ export class TR808Kick {
         masterGain.connect(this.destination);
 
         // Micro-randomization using shared utilities
-        const tuneDrift = applyPitchDrift(tune, 1.0);
+        const tuneDrift = applyPitchDrift(tune, 2.0); // 2 cents drift
         const finalDecay = applyVariance(decayTime, 0.02);
 
+        // Two-stage damping requires the final decay to be longer than the damping stage (20ms)
+        const safeFinalDecay = Math.max(finalDecay, 0.03);
+
         // Pitch Envelope: Start high (Tune * 2.5) and drop quickly (50ms) to simulate the membrane hit ('tonk')
-        // This rapid sweep generates the punch without needing a separate click oscillator
         const startFreq = tuneDrift * 2.5;
         const endFreq = tuneDrift;
 
         osc.frequency.setValueAtTime(startFreq, time);
         osc.frequency.exponentialRampToValueAtTime(endFreq, time + 0.05);
 
-        // VCA Amp Envelope: Instant attack, adjustable exponential decay
-        masterGain.gain.setValueAtTime(velocity, time);
-        masterGain.gain.exponentialRampToValueAtTime(0.001, time + finalDecay);
+        // VCA Amp Envelope: Two-stage damping emulating diode behavior
+        const v = Math.max(0.001, velocity);
+        masterGain.gain.setValueAtTime(v, time);
+
+        // Stage 1: Fast initial damping (20ms) to 50% volume
+        masterGain.gain.exponentialRampToValueAtTime(Math.max(0.001, v * 0.5), time + 0.02);
+
+        // Stage 2: Main exponential decay
+        masterGain.gain.exponentialRampToValueAtTime(0.001, time + safeFinalDecay);
 
-        osc.start(time).stop(time + finalDecay);
+        osc.start(time).stop(time + safeFinalDecay);
 
         osc.onstop = () => {
             osc.dispose();

src/logic/drums/TR808Snare.ts

@@ -1,20 +1,16 @@
 import * as Tone from 'tone'
-import { applyPitchDrift, applyVariance } from '../DrumUtils'
+import { applyPitchDrift, applyVariance, generateWhiteNoise } from '../DrumUtils'
 
 export class TR808Snare {
     private noiseBuffer: AudioBuffer;
 
     constructor(private destination: Tone.ToneAudioNode) {
-        const sampleRate = Tone.getContext().sampleRate;
-        const bufferSize = sampleRate * 0.5; // 500ms
-        this.noiseBuffer = Tone.getContext().createBuffer(1, bufferSize, sampleRate);
-        const data = this.noiseBuffer.getChannelData(0);
-        for (let i = 0; i < data.length; i++) {
-            data[i] = Math.random() * 2 - 1;
-        }
+        this.noiseBuffer = generateWhiteNoise(Tone.getContext());
     }
 
     trigger(time: number, pitch: number, snappy: number, velocity: number = 0.8) {
+        if (velocity <= 0) return;
+
         // pitch maps to tone balance here (balance between low and high modes)
         const toneBalance = pitch;
 
@@ -25,8 +21,8 @@ export class TR808Snare {
         const noiseFilterFreq = applyVariance(1800, 0.02);
 
         // 808 Membrane modes: fixed at ~238Hz and ~476Hz according to research
-        const oscLow = new Tone.Oscillator(applyPitchDrift(238, 1.0), "sine");
-        const oscHigh = new Tone.Oscillator(applyPitchDrift(476, 1.0), "sine");
+        const oscLow = new Tone.Oscillator(applyPitchDrift(238, 2.0), "sine");
+        const oscHigh = new Tone.Oscillator(applyPitchDrift(476, 2.0), "sine");
         oscLow.phase = Math.random() * 360;
         oscHigh.phase = Math.random() * 360;
 
@@ -40,16 +36,19 @@ export class TR808Snare {
 
         // Independent envelopes for maximum authenticity as per research
         // High mode decays faster (approx 75% of low mode decay)
-        gainLow.gain.setValueAtTime(velocity * (1 - toneBalance), time);
+        const v = Math.max(0.001, velocity);
+        gainLow.gain.setValueAtTime(v * (1 - toneBalance), time);
         gainLow.gain.exponentialRampToValueAtTime(0.001, time + vcaDecay);
 
-        gainHigh.gain.setValueAtTime(velocity * toneBalance, time);
+        gainHigh.gain.setValueAtTime(v * toneBalance, time);
         gainHigh.gain.exponentialRampToValueAtTime(0.001, time + vcaDecay * 0.75);
 
         // Snappy Layer
         const noiseSrc = new Tone.BufferSource(this.noiseBuffer);
+        // Random start offset to avoid machine-gun effect
+        const randomStart = Math.random() * (this.noiseBuffer.duration - snappyDecay - 0.1);
+
         // High-pass filter (>1800Hz) to prevent phase trap with tonal body
-        // Q = 0.707 (Butterworth)
         const noiseFilter = new Tone.Filter({
             frequency: noiseFilterFreq,
             type: "highpass",
@@ -61,12 +60,12 @@ export class TR808Snare {
         noiseFilter.connect(snappyGain);
         snappyGain.connect(this.destination);
 
-        snappyGain.gain.setValueAtTime(velocity * 0.8, time);
+        snappyGain.gain.setValueAtTime(v * 0.8, time);
         snappyGain.gain.exponentialRampToValueAtTime(0.001, time + snappyDecay);
 
         oscLow.start(time).stop(time + vcaDecay);
         oscHigh.start(time).stop(time + vcaDecay);
-        noiseSrc.start(time).stop(time + snappyDecay + 0.1);
+        noiseSrc.start(time, randomStart).stop(time + snappyDecay + 0.1);
 
         // Cleanup
         oscLow.onstop = () => {

src/logic/drums/TR909Kick.ts

@@ -1,5 +1,5 @@
 import * as Tone from 'tone'
-import { makeDistortionCurve, applyPitchDrift, applyVariance } from '../DrumUtils'
+import { makeDistortionCurve, applyPitchDrift, applyVariance, generateWhiteNoise } from '../DrumUtils'
 
 export class TR909Kick {
     private noiseBuffer: AudioBuffer;
@@ -8,17 +8,12 @@ export class TR909Kick {
     constructor(private destination: Tone.ToneAudioNode) {
         // Soft Clipping curve from research
         this.bodyCurve = makeDistortionCurve(10);
-
-        const sampleRate = Tone.getContext().sampleRate;
-        const bufferSize = sampleRate * 0.05; // 50ms click
-        this.noiseBuffer = Tone.getContext().createBuffer(1, bufferSize, sampleRate);
-        const data = this.noiseBuffer.getChannelData(0);
-        for (let i = 0; i < bufferSize; i++) {
-            data[i] = Math.random() * 2 - 1;
-        }
+        this.noiseBuffer = generateWhiteNoise(Tone.getContext());
     }
 
     trigger(time: number, pitch: number, decay: number, velocity: number = 0.8) {
+        if (velocity <= 0) return;
+
         // 909 Kick base frequency is fixed around 50Hz
         const tune = 50;
         // The 'Pitch' parameter on 909 maps to the frequency sweep duration
@@ -28,7 +23,7 @@ export class TR909Kick {
         const decayTime = 0.3 + decay * 0.3;
 
         // Micro-randomization using shared utilities
-        const tuneDrift = applyPitchDrift(tune, 0.5);
+        const tuneDrift = applyPitchDrift(tune, 0.5); // 0.5 cents drift
         const vcaDecay = applyVariance(decayTime, 0.02);
         const noiseFilterFreq = applyVariance(1000, 0.02);
 
@@ -53,11 +48,14 @@ export class TR909Kick {
         bodyOsc.frequency.exponentialRampToValueAtTime(endFreq, time + sweepDuration);
 
         // VCA Envelope
-        bodyGain.gain.setValueAtTime(velocity, time);
+        const v = Math.max(0.001, velocity);
+        bodyGain.gain.setValueAtTime(v, time);
         bodyGain.gain.exponentialRampToValueAtTime(0.001, time + vcaDecay);
 
         // Click Layer (Noise)
         const noiseSrc = new Tone.BufferSource(this.noiseBuffer);
+        const randomStart = Math.random() * (this.noiseBuffer.duration - 0.1);
+
         const noiseFilter = new Tone.Filter(noiseFilterFreq, "highpass"); // HPF > 1kHz to avoid phase trap
         const noiseGain = new Tone.Gain(0);
 
@@ -67,7 +65,7 @@ export class TR909Kick {
 
         // Ultra short envelope (10-20ms) for the click
         const clickDecay = applyVariance(0.02, 0.02);
-        noiseGain.gain.setValueAtTime(velocity * 0.7, time);
+        noiseGain.gain.setValueAtTime(v * 0.7, time);
         noiseGain.gain.exponentialRampToValueAtTime(0.001, time + clickDecay);
 
         // Rectangular Pulse Click: Short 5ms impulse for attack articulation
@@ -76,11 +74,11 @@ export class TR909Kick {
         pulseOsc.connect(pulseGain);
         pulseGain.connect(this.destination);
 
-        pulseGain.gain.setValueAtTime(velocity * 0.5, time);
+        pulseGain.gain.setValueAtTime(v * 0.5, time);
         pulseGain.gain.exponentialRampToValueAtTime(0.001, time + 0.005);
 
         bodyOsc.start(time).stop(time + vcaDecay);
-        noiseSrc.start(time).stop(time + clickDecay);
+        noiseSrc.start(time, randomStart).stop(time + clickDecay);
         pulseOsc.start(time).stop(time + 0.005);
 
         bodyOsc.onstop = () => {