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// MQ Synthesizer
// Harmonic oscillator bank for sinusoidal synthesis, plus two-pole resonator mode
// Deterministic LCG PRNG
function randFloat(seed, min, max) {
seed = (1664525 * seed + 1013904223) % 0x100000000;
return min + (seed / 0x100000000) * (max - min);
}
// Build harmonic list from harmonics config.
// Fundamental (ratio=1.0, ampMult=1.0) is always first.
// Then harmonics at n*freq_mult for n=1,2,... with ampMult=decay^n (added on top).
function buildHarmonics(harmonics) {
const decay = Math.min(harmonics.decay ?? 0.0, 0.90);
const freqMult = harmonics.freq_mult ?? 2.0;
const result = [{ ratio: 1.0, ampMult: 1.0 }]; // fundamental always
if (decay > 0) {
for (let n = 1; ; ++n) {
const ampMult = Math.pow(decay, n);
if (ampMult < 0.001) break;
result.push({ ratio: n * freqMult, ampMult });
}
}
return result;
}
// Synthesize audio from MQ partials
// partials: array of {freqCurve (with a0-a3 for amp), harmonics?, resonator?}
// harmonics: {decay, freq_mult, jitter, spread}
// resonator: {enabled, r, gainComp} — two-pole resonator mode per partial
// integratePhase: true = accumulate 2π*f/SR per sample (correct for varying freq)
// false = 2π*f*t (simpler, only correct for constant freq)
// options.k1: LP coefficient in (0,1] — omit to bypass
// options.k2: HP coefficient in (0,1] — omit to bypass
function synthesizeMQ(partials, sampleRate, duration, integratePhase = true, options = {}) {
const numSamples = Math.floor(sampleRate * duration);
const pcm = new Float32Array(numSamples);
const defaultHarmonics = {
decay: 0.0,
freq_mult: 1.0,
jitter: 0.05,
spread: 0.02
};
// Pre-build per-partial configs with fixed spread/jitter and phase accumulators
const configs = [];
for (let p = 0; p < partials.length; ++p) {
const partial = partials[p];
const fc = partial.freqCurve;
if ((partial.resonator && partial.resonator.enabled) || options.forceResonator) {
// --- Two-pole resonator mode ---
// Driven by band-limited noise scaled by amp curve.
// r controls pole radius (bandwidth): r→1 = narrow, r→0 = wide.
// gainNorm = sqrt(1 - r²) normalises steady-state output power to ~A.
const res = partial.resonator || {};
const r = options.forceRGain ? clamp(options.globalR, 0, 0.9999)
: (res.r != null ? clamp(res.r, 0, 0.9999) : 0.995);
const gainComp = options.forceRGain ? options.globalGain
: (res.gainComp != null ? res.gainComp : 1.0);
const gainNorm = Math.sqrt(Math.max(0, 1.0 - r * r));
// Build harmonic list (jitter/spread not applied to resonator)
const harm = partial.harmonics || defaultHarmonics;
const harmonicList = buildHarmonics(harm);
configs.push({
mode: 'resonator',
fc,
r, gainComp, gainNorm,
harmonicList,
y1: new Float64Array(harmonicList.length),
y2: new Float64Array(harmonicList.length),
noiseSeed: ((p * 1664525 + 1013904223) & 0xFFFFFFFF) >>> 0
});
} else {
// --- Sinusoidal (harmonic) mode ---
const harm = partial.harmonics || defaultHarmonics;
const spread = harm.spread ?? 0.0;
const jitter = harm.jitter ?? 0.0;
const harmonicList = buildHarmonics(harm);
const replicaData = [];
for (let h = 0; h < harmonicList.length; ++h) {
const hc = harmonicList[h];
const spreadVal = randFloat(p * 67890 + h * 999, -spread, spread);
const initPhase = randFloat(p * 67890 + h, 0.0, 1.0) * jitter * 2.0 * Math.PI;
replicaData.push({ ratio: hc.ratio, ampMult: hc.ampMult, spread: spreadVal, phase: initPhase });
}
configs.push({ mode: 'sinusoid', fc, replicaData });
}
}
for (let i = 0; i < numSamples; ++i) {
const t = i / sampleRate;
let sample = 0.0;
for (let p = 0; p < configs.length; ++p) {
const cfg = configs[p];
const {fc} = cfg;
if (cfg.mode === 'resonator') {
if (t < fc.t0 || t > fc.t3) {
cfg.y1.fill(0.0); cfg.y2.fill(0.0); continue;
}
const f0 = evalBezier(fc, t);
const A = evalBezierAmp(fc, t);
// LCG noise excitation (deterministic per-partial, shared across harmonics)
cfg.noiseSeed = (Math.imul(1664525, cfg.noiseSeed) + 1013904223) >>> 0;
const noise = cfg.noiseSeed / 0x100000000 * 2.0 - 1.0;
for (let h = 0; h < cfg.harmonicList.length; ++h) {
const hc = cfg.harmonicList[h];
const fh = f0 * hc.ratio;
const omega = 2.0 * Math.PI * fh / sampleRate;
const b1 = 2.0 * cfg.r * Math.cos(omega);
const x = A * cfg.gainNorm * noise * hc.ampMult;
const y = b1 * cfg.y1[h] - cfg.r * cfg.r * cfg.y2[h] + x;
cfg.y2[h] = cfg.y1[h];
cfg.y1[h] = y;
sample += y * cfg.gainComp;
}
} else {
if (t < fc.t0 || t > fc.t3) continue;
const f0 = evalBezier(fc, t);
const A0 = evalBezierAmp(fc, t);
for (let h = 0; h < cfg.replicaData.length; ++h) {
const rep = cfg.replicaData[h];
const f = f0 * rep.ratio * (1.0 + rep.spread);
const A = A0 * rep.ampMult;
let phase;
if (integratePhase) {
rep.phase += 2.0 * Math.PI * f / sampleRate;
phase = rep.phase;
} else {
phase = 2.0 * Math.PI * f * t + rep.phase;
}
sample += A * Math.sin(phase);
}
}
}
pcm[i] = sample;
}
// Post-synthesis filters (applied before normalization)
// LP: y[n] = k1*x[n] + (1-k1)*y[n-1] — options.k1 in (0,1], omit to bypass
// HP: y[n] = k2*(y[n-1] + x[n] - x[n-1]) — options.k2 in (0,1], omit to bypass
if (options.k1 != null) {
const k1 = clamp(options.k1, 0, 1);
let y = 0.0;
for (let i = 0; i < numSamples; ++i) {
y = k1 * pcm[i] + (1.0 - k1) * y;
pcm[i] = y;
}
}
if (options.k2 != null) {
const k2 = clamp(options.k2, 0, 1);
let y = 0.0, xp = 0.0;
for (let i = 0; i < numSamples; ++i) {
const x = pcm[i];
y = k2 * (y + x - xp);
xp = x;
pcm[i] = y;
}
}
// Normalize
let maxAbs = 0;
for (let i = 0; i < numSamples; ++i) maxAbs = Math.max(maxAbs, Math.abs(pcm[i]));
if (maxAbs > 1.0) {
for (let i = 0; i < numSamples; ++i) pcm[i] /= maxAbs;
}
return pcm;
}
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