Authentic Analog Drum Synthesis Implementation

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 rangeCents - Drift range in cents (default 2.0)
  */
-export function applyPitchDrift(base: number, range: number = 1.0): number {
-    return base + (Math.random() * 2 - 1) * range;
+export function applyPitchDrift(base: number, rangeCents: number = 2.0): number {
+    const cents = (Math.random() * 2 - 1) * rangeCents;
+    return base * Math.pow(2, cents / 1200);
 }
 
 /**
@@ -37,6 +40,38 @@ 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]
     return base * (1 + (Math.random() * (variance * 2) - variance));
 }
+
+/**
+ * Generates a 2.0s white noise buffer.
+ */
+export function generateWhiteNoise(context: Tone.BaseContext): AudioBuffer {
+    const sampleRate = context.sampleRate;
+    const bufferSize = sampleRate * 2.0;
+    const buffer = context.createBuffer(1, bufferSize, sampleRate);
+    const data = buffer.getChannelData(0);
+    for (let i = 0; i < bufferSize; i++) {
+        data[i] = Math.random() * 2 - 1;
+    }
+    return buffer;
+}
+
+/**
+ * Generates a 15-bit LFSR pseudo-random noise buffer (x^15 + x^14 + 1).
+ * Emulates vintage digital textures (e.g., TR-909 Snappy).
+ */
+export function generateLFSRNoise(context: Tone.BaseContext): AudioBuffer {
+    const sampleRate = context.sampleRate;
+    const bufferSize = sampleRate * 2.0;
+    const buffer = context.createBuffer(1, bufferSize, sampleRate);
+    const data = buffer.getChannelData(0);
+    let lfsr = 0x7FFF; // 15-bit initial state
+
+    for (let i = 0; i < bufferSize; i++) {
+        const bit = ((lfsr >> 14) ^ (lfsr >> 13)) & 1;
+        lfsr = ((lfsr << 1) | bit) & 0x7FFF;
+        data[i] = (lfsr / 16384.0) - 1.0;
+    }
+    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;
+        const context = Tone.getContext();
+        this.noiseBuffer = generateWhiteNoise(context);
     }
 
     trigger(time: number, pitch: number, decay: number, velocity: number = 0.8) {
+        const safeVelocity = Math.max(0.001, velocity);
         const noiseSrc = new Tone.BufferSource(this.noiseBuffer);
         const bpfFreq = (1000 + pitch * 1000);
         const bpf = new Tone.Filter(applyVariance(bpfFreq, 0.02), "bandpass");
@@ -27,19 +26,21 @@ export class TR808Clap {
 
         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(safeVelocity, snapTime);
+            gain.gain.exponentialRampToValueAtTime(safeVelocity * 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(safeVelocity, finalDecayStart);
         gain.gain.exponentialRampToValueAtTime(0.001, finalDecayStart + decayTime);
 
-        noiseSrc.start(time).stop(finalDecayStart + decayTime);
+        // Use random offset to avoid "machine-gun" effect
+        const randomStart = Math.random() * (this.noiseBuffer.duration - 0.6);
+        noiseSrc.start(time, randomStart).stop(finalDecayStart + decayTime);
 
         noiseSrc.onended = () => {
             noiseSrc.dispose();

src/logic/drums/TR808Cowbell.ts

@@ -2,11 +2,12 @@ import * as Tone from 'tone'
 import { applyPitchDrift, applyVariance } from '../DrumUtils'
 
 export class TR808Cowbell {
-    private activeGains: Set<Tone.Gain> = new Set();
+    private activeVoices: Set<{ oscillators: Tone.Oscillator[], gain: Tone.Gain }> = new Set();
 
     constructor(private destination: Tone.ToneAudioNode) { }
 
     trigger(time: number, pitch: number, decay: number, velocity: number = 0.8) {
+        const safeVelocity = Math.max(0.001, velocity);
         // 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
@@ -30,10 +31,11 @@ export class TR808Cowbell {
 
         const decayTime = applyVariance(0.1 + decay * 0.4, 0.02);
 
-        vca.gain.setValueAtTime(velocity, time);
+        vca.gain.setValueAtTime(safeVelocity, time);
         vca.gain.exponentialRampToValueAtTime(0.001, time + decayTime);
 
-        this.activeGains.add(vca);
+        const voice = { oscillators: [osc1, osc2], gain: vca };
+        this.activeVoices.add(voice);
 
         osc1.start(time).stop(time + decayTime);
         osc2.start(time).stop(time + decayTime);
@@ -45,15 +47,16 @@ export class TR808Cowbell {
             bpf.dispose();
             hpf.dispose();
             vca.dispose();
-            this.activeGains.delete(vca);
+            this.activeVoices.delete(voice);
         };
     }
 
     stop(time: number) {
-        this.activeGains.forEach(vca => {
-            vca.gain.cancelScheduledValues(time);
-            vca.gain.exponentialRampToValueAtTime(0.001, time + 0.02);
+        this.activeVoices.forEach(voice => {
+            voice.gain.gain.cancelScheduledValues(time);
+            voice.gain.gain.exponentialRampToValueAtTime(0.001, time + 0.02);
+            voice.oscillators.forEach(osc => osc.stop(time + 0.02));
         });
-        this.activeGains.clear();
+        this.activeVoices.clear();
     }
 }

src/logic/drums/TR808HiHat.ts

@@ -3,11 +3,12 @@ import { applyPitchDrift, applyVariance } from '../DrumUtils'
 
 export class TR808HiHat {
     private frequencies = [205.3, 304.4, 369.6, 522.7, 800, 540];
-    private activeGains: Set<Tone.Gain> = new Set();
+    private activeVoices: Set<{ oscillators: Tone.Oscillator[], gain: Tone.Gain }> = new Set();
 
     constructor(private destination: Tone.ToneAudioNode) { }
 
     trigger(time: number, isOpen: boolean, pitch: number, decay: number, velocity: number = 0.8) {
+        const safeVelocity = Math.max(0.001, velocity);
         // Create nodes
         const mixGain = new Tone.Gain(0.15);
         const bpf1 = new Tone.Filter(3440, "bandpass");
@@ -48,34 +49,35 @@ export class TR808HiHat {
         const decayTime = applyVariance(decayBase, 0.02);
 
         // VCA Envelope
-        envGain.gain.setValueAtTime(velocity, time);
+        envGain.gain.setValueAtTime(safeVelocity, time);
         envGain.gain.exponentialRampToValueAtTime(0.001, time + decayTime);
 
-        this.activeGains.add(envGain);
+        const voice = { oscillators, gain: envGain };
+        this.activeVoices.add(voice);
 
         // Scheduling
         oscillators.forEach(osc => {
             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();
             bpf1.dispose();
             bpf2.dispose();
             envGain.dispose();
             hpf.dispose();
-            this.activeGains.delete(envGain);
+            this.activeVoices.delete(voice);
         };
     }
 
     stop(time: number) {
-        this.activeGains.forEach(gain => {
-            gain.gain.cancelScheduledValues(time);
-            gain.gain.exponentialRampToValueAtTime(0.001, time + 0.02);
+        this.activeVoices.forEach(voice => {
+            voice.gain.gain.cancelScheduledValues(time);
+            voice.gain.gain.exponentialRampToValueAtTime(0.001, time + 0.02);
+            voice.oscillators.forEach(osc => osc.stop(time + 0.02));
         });
-        this.activeGains.clear();
+        this.activeVoices.clear();
     }
 }

src/logic/drums/TR808Kick.ts

@@ -19,22 +19,28 @@ export class TR808Kick {
         masterGain.connect(this.destination);
 
         // Micro-randomization using shared utilities
-        const tuneDrift = applyPitchDrift(tune, 1.0);
+        const tuneDrift = applyPitchDrift(tune, 2.0);
         const finalDecay = applyVariance(decayTime, 0.02);
 
         // 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: Instant attack, two-stage decay (diode damping)
+        // Stage 1: Fast 20ms initial decay to 50% volume
+        // Stage 2: Main exponential decay to silent
+        const safeVelocity = Math.max(0.001, velocity);
+        const dampingTime = 0.02;
+        const safeFinalDecay = Math.max(dampingTime + 0.01, finalDecay);
 
-        osc.start(time).stop(time + finalDecay);
+        masterGain.gain.setValueAtTime(safeVelocity, time);
+        masterGain.gain.exponentialRampToValueAtTime(safeVelocity * 0.5, time + dampingTime);
+        masterGain.gain.exponentialRampToValueAtTime(0.001, time + safeFinalDecay);
+
+        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;
-        }
+        const context = Tone.getContext();
+        this.noiseBuffer = generateWhiteNoise(context);
     }
 
     trigger(time: number, pitch: number, snappy: number, velocity: number = 0.8) {
+        const safeVelocity = Math.max(0.001, velocity);
         // 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 +36,14 @@ 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);
+        gainLow.gain.setValueAtTime(safeVelocity * (1 - toneBalance), time);
         gainLow.gain.exponentialRampToValueAtTime(0.001, time + vcaDecay);
 
-        gainHigh.gain.setValueAtTime(velocity * toneBalance, time);
+        gainHigh.gain.setValueAtTime(safeVelocity * toneBalance, time);
         gainHigh.gain.exponentialRampToValueAtTime(0.001, time + vcaDecay * 0.75);
 
         // Snappy Layer
         const noiseSrc = new Tone.BufferSource(this.noiseBuffer);
-        // 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 +55,14 @@ export class TR808Snare {
         noiseFilter.connect(snappyGain);
         snappyGain.connect(this.destination);
 
-        snappyGain.gain.setValueAtTime(velocity * 0.8, time);
+        snappyGain.gain.setValueAtTime(safeVelocity * 0.8, time);
         snappyGain.gain.exponentialRampToValueAtTime(0.001, time + snappyDecay);
 
+        const randomStart = Math.random() * (this.noiseBuffer.duration - 0.5);
+        noiseSrc.start(time, randomStart).stop(time + snappyDecay + 0.1);
+
         oscLow.start(time).stop(time + vcaDecay);
         oscHigh.start(time).stop(time + vcaDecay);
-        noiseSrc.start(time).stop(time + snappyDecay + 0.1);
 
         // Cleanup
         oscLow.onstop = () => {