strudel/packages/superdough/synth.mjs

import { midiToFreq, noteToMidi } from './util.mjs';
import { registerSound, getAudioContext } from './superdough.mjs';
import { gainNode, getEnvelope, getExpEnvelope } from './helpers.mjs';

const mod = (freq, range = 1, type = 'sine') => {
  const ctx = getAudioContext();
  const osc = ctx.createOscillator();
  osc.type = type;
  osc.frequency.value = freq;
  osc.start();
  const g = new GainNode(ctx, { gain: range });
  osc.connect(g); // -range, range
  return { node: g, stop: (t) => osc.stop(t) };
};

const fm = (osc, harmonicityRatio, modulationIndex, wave = 'sine') => {
  const carrfreq = osc.frequency.value;
  const modfreq = carrfreq * harmonicityRatio;
  const modgain = modfreq * modulationIndex;
  return mod(modfreq, modgain, wave);
};


export function registerSynthSounds() {
  ['sine', 'square', 'triangle',
    'sawtooth', 'pink', 'white',
    'brown'].forEach((wave) => {
      registerSound(
        wave,
        (t, value, onended) => {
          // destructure adsr here, because the default should be different for synths and samples
          let {
            attack = 0.001,
            decay = 0.05,
            sustain = 0.6,
            release = 0.01,
            fmh: fmHarmonicity = 1,
            fmi: fmModulationIndex,
            fmenv: fmEnvelopeType = 'lin',
            fmattack: fmAttack,
            fmdecay: fmDecay,
            fmsustain: fmSustain,
            fmrelease: fmRelease,
            fmvelocity: fmVelocity,
            fmwave: fmWaveform = 'sine',
            vib = 0,
            vibmod = 0.5,
            noise = 0,
          } = value;
          let { n, note, freq } = value;
          // with synths, n and note are the same thing
          note = note || 36;
          if (typeof note === 'string') {
            note = noteToMidi(note); // e.g. c3 => 48
          }
          // get frequency
          if (!freq && typeof note === 'number') {
            freq = midiToFreq(note); // + 48);
          }
          // maybe pull out the above frequency resolution?? (there is also getFrequency but it has no default)
          // make oscillator
          const { node: o, stop, dry_node = null } = getOscillator({
            t,
            s: wave,
            freq,
            vib,
            vibmod,
            partials: n,
            noise: noise,
          });
          // FM + FM envelope
          let stopFm, fmEnvelope;
          if (fmModulationIndex) {
            const { node: modulator, stop } = fm(dry_node !== null ? dry_node : o, fmHarmonicity, fmModulationIndex, fmWaveform);
            if (![fmAttack, fmDecay, fmSustain, fmRelease, fmVelocity].find((v) => v !== undefined)) {
              // no envelope by default
              modulator.connect(dry_node !== null ? dry_node.frequency : o.frequency);
            } else {
              fmAttack = fmAttack ?? 0.001;
              fmDecay = fmDecay ?? 0.001;
              fmSustain = fmSustain ?? 1;
              fmRelease = fmRelease ?? 0.001;
              fmVelocity = fmVelocity ?? 1;
              fmEnvelope = getEnvelope(fmAttack, fmDecay, fmSustain, fmRelease, fmVelocity, t);
              if (fmEnvelopeType === 'exp') {
                fmEnvelope = getExpEnvelope(fmAttack, fmDecay, fmSustain, fmRelease, fmVelocity, t);
                fmEnvelope.node.maxValue = fmModulationIndex * 2;
                fmEnvelope.node.minValue = 0.00001;
              }
              modulator.connect(fmEnvelope.node);
              fmEnvelope.node.connect(dry_node !== null ? dry_node.frequency : o.frequency);
            }
            stopFm = stop;
          }

          // turn down
          const g = gainNode(0.3);

          // gain envelope
          const { node: envelope, stop: releaseEnvelope } = getEnvelope(attack, decay, sustain, release, 1, t);

          o.onended = () => {
            o.disconnect();
            g.disconnect();
            onended();
          };
          return {
            node: o.connect(g).connect(envelope),
            stop: (releaseTime) => {
              releaseEnvelope(releaseTime);
              fmEnvelope?.stop(releaseTime);
              let end = releaseTime + release;
              stop(end);
              stopFm?.(end);
            },
          };
        },
        { type: 'synth', prebake: true },
      );
    });
}

export function waveformN(partials, type) {
  const real = new Float32Array(partials + 1);
  const imag = new Float32Array(partials + 1);
  const ac = getAudioContext();
  const osc = ac.createOscillator();

  const amplitudes = {
    sawtooth: (n) => 1 / n,
    square: (n) => (n % 2 === 0 ? 0 : 1 / n),
    triangle: (n) => (n % 2 === 0 ? 0 : 1 / (n * n)),
  };

  if (!amplitudes[type]) {
    throw new Error(`unknown wave type ${type}`);
  }

  real[0] = 0; // dc offset
  imag[0] = 0;
  let n = 1;
  while (n <= partials) {
    real[n] = amplitudes[type](n);
    imag[n] = 0;
    n++;
  }

  const wave = ac.createPeriodicWave(real, imag);
  osc.setPeriodicWave(wave);
  return osc;
}

export function getNoiseOscillator({ t, ac, type = 'white' }) {
  const bufferSize = 2 * ac.sampleRate;
  const noiseBuffer = ac.createBuffer(1, bufferSize, ac.sampleRate);
  const output = noiseBuffer.getChannelData(0);
  let lastOut = 0;
  let b0, b1, b2, b3, b4, b5, b6;
  b0 = b1 = b2 = b3 = b4 = b5 = b6 = 0.0;

  for (let i = 0; i < bufferSize; i++) {
    if (type === 'white') {
      output[i] = Math.random() * 2 - 1;
    } else if (type === 'brown') {
      let white = Math.random() * 2 - 1;
      output[i] = (lastOut + (0.02 * white)) / 1.02;
      lastOut = output[i];
    } else if (type === 'pink') {
      let white = Math.random() * 2 - 1;
      b0 = 0.99886 * b0 + white * 0.0555179;
      b1 = 0.99332 * b1 + white * 0.0750759;
      b2 = 0.96900 * b2 + white * 0.1538520;
      b3 = 0.86650 * b3 + white * 0.3104856;
      b4 = 0.55000 * b4 + white * 0.5329522;
      b5 = -0.7616 * b5 - white * 0.0168980;
      output[i] = b0 + b1 + b2 + b3 + b4 + b5 + b6 + white * 0.5362;
      output[i] *= 0.11;
      b6 = white * 0.115926;
    }
  }

  const o = ac.createBufferSource();
  o.buffer = noiseBuffer;
  o.loop = true;
  o.start(t);

  return {
    node: o,
    stop: (time) => o.stop(time)
  };
}

export function getOscillator({ s, freq, t, vib, vibmod, partials, noise }) {
  // Make oscillator with partial count
  let ac = getAudioContext();
  let o;

  if (['pink', 'white', 'brown'].includes(s)) {
    let noiseOscillator = getNoiseOscillator({ t: t, ac: getAudioContext(), type: s })
    return {
      node: noiseOscillator.node,
      stop: noiseOscillator.stop
    }
  } else {
    if (!partials || s === 'sine') {
      o = getAudioContext().createOscillator();
      o.type = s || 'triangle';
    } else {
      o = waveformN(partials, s);
    }
    o.frequency.value = Number(freq);
    o.start(t);

    // Additional oscillator for vibrato effect
    let vibrato_oscillator;
    if (vib > 0) {
      vibrato_oscillator = getAudioContext().createOscillator();
      vibrato_oscillator.frequency.value = vib;
      const gain = getAudioContext().createGain();
      // Vibmod is the amount of vibrato, in semitones
      gain.gain.value = vibmod * 100;
      vibrato_oscillator.connect(gain);
      gain.connect(o.detune);
      vibrato_oscillator.start(t);
    }

    if (noise > 0) {
      // Two gain nodes to set the oscillators to their respective levels
      noise = noise > 1 ? 1 : noise;
      let o_gain = ac.createGain();
      let n_gain = ac.createGain();
      o_gain.gain.setValueAtTime(1 - noise, ac.currentTime);
      n_gain.gain.setValueAtTime(noise, ac.currentTime);

      // Instanciating a mixer to blend sources together
      let mix_gain = ac.createGain();

      // Connecting the main oscillator to the gain node
      o.connect(o_gain).connect(mix_gain);

      // Instanciating a noise oscillator and connecting 
      const noiseOscillator = getNoiseOscillator({ t: t, ac: ac, type: 'pink' });
      noiseOscillator.node.connect(n_gain).connect(mix_gain);

      return {
        node: mix_gain,
        dry_node: o,
        stop: (time) => {
          vibrato_oscillator?.stop(time);
          o.stop(time);
          noiseOscillator.stop(time);
        }
      }
    }

    return {
      node: o,
      stop: (time) => {
        vibrato_oscillator?.stop(time);
        o.stop(time);
      },
    };
  }
}