Implement research-based analog drum synthesis refinements

src/logic/DrumMachine.ts

@@ -99,6 +99,17 @@ export class DrumMachine {
         this.params[drum] = { pitch, decay }
     }
 
+    /**
+     * Synchronizes all internal parameters with the provided state.
+     */
+    syncInternalParams(kit: '808' | '909', saturation: number, drumParams: Record<string, { pitch: number, decay: number }>) {
+        this.setKit(kit)
+        this.setSaturation(saturation)
+        Object.entries(drumParams).forEach(([id, p]) => {
+            this.setDrumParams(id, p.pitch, p.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.
  */
@@ -40,3 +42,36 @@ 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 an authentic 15-bit LFSR noise buffer (TR-909 style).
+ * Polynomial: x^15 + x^14 + 1
+ */
+export function generateLFSRNoise(context: Tone.BaseContext): AudioBuffer {
+    const sampleRate = context.sampleRate;
+    const duration = 2.0;
+    const buffer = context.createBuffer(1, sampleRate * duration, sampleRate);
+    const data = buffer.getChannelData(0);
+
+    let state = 0x7FFF; // 15-bit seed
+    for (let i = 0; i < data.length; i++) {
+        // x^15 + x^14 + 1
+        const bit = ((state >> 14) ^ (state >> 13)) & 1;
+        state = ((state << 1) | bit) & 0x7FFF;
+        data[i] = (state / 0x7FFF) * 2 - 1;
+    }
+    return buffer;
+}
+
+/**
+ * Generates a high-quality white noise buffer.
+ */
+export function generateWhiteNoise(context: Tone.BaseContext, duration: number = 2.0): AudioBuffer {
+    const sampleRate = context.sampleRate;
+    const buffer = context.createBuffer(1, sampleRate * duration, sampleRate);
+    const data = buffer.getChannelData(0);
+    for (let i = 0; i < data.length; i++) {
+        data[i] = Math.random() * 2 - 1;
+    }
+    return buffer;
+}

src/logic/drums/TR808Clap.ts

@@ -12,6 +12,7 @@ export class TR808Clap {
     }
 
     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");

src/logic/drums/TR808Cowbell.ts

@@ -7,6 +7,7 @@ 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

src/logic/drums/TR808HiHat.ts

@@ -8,6 +8,7 @@ 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");

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
@@ -30,11 +32,17 @@ export class TR808Kick {
         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 "diode damping" emulation
+        // Stage 1: Fast 20ms initial decay to 50% volume (emulates diode resistance shift)
+        // Stage 2: Final decay (Tone.js requires values > 0 for exponentialRamp)
+        const dampingTime = 0.02;
+        const safeFinalDecay = Math.max(dampingTime + 0.01, finalDecay);
+
+        masterGain.gain.setValueAtTime(Math.max(0.001, velocity), time);
+        masterGain.gain.exponentialRampToValueAtTime(Math.max(0.001, velocity * 0.5), time + dampingTime);
+        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 +1,15 @@
 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(), 2.0);
     }
 
     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;
 
@@ -48,6 +43,7 @@ export class TR808Snare {
 
         // Snappy Layer
         const noiseSrc = new Tone.BufferSource(this.noiseBuffer);
+        const randomStart = Math.random() * (this.noiseBuffer.duration - 0.5);
         // High-pass filter (>1800Hz) to prevent phase trap with tonal body
         // Q = 0.707 (Butterworth)
         const noiseFilter = new Tone.Filter({
@@ -66,7 +62,7 @@ export class TR808Snare {
 
         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

@@ -1,24 +1,18 @@
 import * as Tone from 'tone'
-import { makeDistortionCurve, applyPitchDrift, applyVariance } from '../DrumUtils'
+import { makeDistortionCurve, applyPitchDrift, applyVariance, generateWhiteNoise } from '../DrumUtils'
 
 export class TR909Kick {
     private noiseBuffer: AudioBuffer;
     private bodyCurve: Float32Array;
 
     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.bodyCurve = makeDistortionCurve(30);
+        this.noiseBuffer = generateWhiteNoise(Tone.getContext(), 2.0);
     }
 
     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
@@ -58,6 +52,8 @@ export class TR909Kick {
 
         // Click Layer (Noise)
         const noiseSrc = new Tone.BufferSource(this.noiseBuffer);
+        // Random start offset to avoid machine-gun effect
+        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);
 
@@ -80,7 +76,7 @@ export class TR909Kick {
         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 = () => {

src/logic/drums/TR909Snare.ts

@@ -1,5 +1,5 @@
 import * as Tone from 'tone'
-import { makeDistortionCurve, applyPitchDrift, applyVariance } from '../DrumUtils'
+import { makeDistortionCurve, applyPitchDrift, applyVariance, generateLFSRNoise } from '../DrumUtils'
 
 export class TR909Snare {
     private noiseBuffer: AudioBuffer;
@@ -8,18 +8,11 @@ export class TR909Snare {
     constructor(private destination: Tone.ToneAudioNode) {
         // Soft Clipping curve from research
         this.bodyCurve = makeDistortionCurve(15);
-
-        const sampleRate = Tone.getContext().sampleRate;
-        const bufferSize = sampleRate * 0.5;
-        this.noiseBuffer = Tone.getContext().createBuffer(1, bufferSize, sampleRate);
-        const data = this.noiseBuffer.getChannelData(0);
-        // While original used LFSR, research says Math.random() is sufficient for Web Audio API context
-        for (let i = 0; i < data.length; i++) {
-            data[i] = Math.random() * 2 - 1;
-        }
+        this.noiseBuffer = generateLFSRNoise(Tone.getContext());
     }
 
     trigger(time: number, pitch: number, snappy: number, velocity: number = 0.8) {
+        if (velocity <= 0) return;
         // 909 Snare Body: 2 triangle oscillators fixed at ~160Hz and ~220Hz
         const freq1 = 160;
         const freq2 = 220;
@@ -50,8 +43,8 @@ export class TR909Snare {
         postShaperGain.connect(tonalGain);
         tonalGain.connect(this.destination);
 
-        // Pitch Sweep: ~320Hz to ~160Hz over 30ms (as per research spec)
-        const sweepTime = 0.03;
+        // Pitch Sweep: ~320Hz to ~160Hz over 50ms (as per research spec)
+        const sweepTime = 0.05;
         const startFreq1 = toneDrift1 * 2;
         const startFreq2 = toneDrift2 * 2;
 
@@ -65,6 +58,7 @@ export class TR909Snare {
 
         // Snappy Layer
         const noiseSrc = new Tone.BufferSource(this.noiseBuffer);
+        const randomStart = Math.random() * (this.noiseBuffer.duration - 0.5);
         const hpf = new Tone.Filter(noiseHPFFreq, "highpass"); // HPF to protect fundamental
         // LPF controlled by 'Tone' (pitch parameter here), range 4kHz to 8kHz (research: toneCutoff)
         const toneCutoff = 4000 + pitch * 4000;
@@ -81,7 +75,7 @@ export class TR909Snare {
 
         osc1.start(time).stop(time + vcaDecay);
         osc2.start(time).stop(time + vcaDecay);
-        noiseSrc.start(time).stop(time + snappyDecay + 0.1);
+        noiseSrc.start(time, randomStart).stop(time + snappyDecay + 0.1);
 
         osc1.onstop = () => {
             osc1.dispose();

src/store/audioStore.ts

@@ -3,6 +3,7 @@ import * as Tone from 'tone'
 import { AcidSynth } from '../logic/AcidSynth'
 import { DrumMachine } from '../logic/DrumMachine'
 import { PadSynth } from '../logic/PadSynth'
+import { useDrumStore } from './instrumentStore'
 
 export interface AudioState {
     isInitialized: boolean
@@ -63,6 +64,17 @@ export const useAudioStore = create<AudioState>((set, get) => ({
         Tone.Transport.bpm.value = get().bpm
         Tone.Transport.swing = get().swing
 
+        // Sync initial drum parameters
+        const drumStore = useDrumStore.getState()
+        drums.syncInternalParams(drumStore.kit, drumStore.drive, {
+            kick: drumStore.kick,
+            snare: drumStore.snare,
+            hihat: drumStore.hihat,
+            hihatOpen: drumStore.hihatOpen,
+            clap: drumStore.clap,
+            cowbell: drumStore.cowbell
+        })
+
         set({
             isInitialized: true,
             bassSynth: bassSynth,