wavepot.js

// https://wavepot.com/

const tau = 2*Math.PI;
const bpm = 132;
const bps = bpm / 60;
const spb = 1 / bps;

function pos(t) {
  const beat = Math.floor(t / spb);
  const frac = (t / spb) % 1.0;
  return [beat, frac];
}

function saw(t, n) {
  let mix = 0;
  for (let i = 1; i <= n; i++) {
    mix += 1/i * Math.sin(t*i);
  }
  return mix;
}

function realsaw(t) {
  return 1-t%1*2;
}

function hz(st) {
  st -= 1;
  return 220 * Math.pow(2, st/12);
}

function bell(t, p) {
  return Math.pow(Math.sin(tau * t * p), 3);
}

function unison(f) {
  function u(t, p) {
    let mix = 0; 
    for (let k =0; k < 4; k ++) mix += f(t, p * (0.99+k*0.006));
    return mix / 4;
  }
  return u;
}

function melody(t) {
  const [beat, frac] = pos(t*2);
  const p = hz([0, 12, 11, 2, 4, 7, 2, 0][beat % 8] + 12);
  const vol = Math.pow(1-frac, 3);
  return unison(bell)(t, p) * vol;
}

function sidechain(t) {
  const frac = pos(t)[1];
  return Math.pow(frac, 1.2);
}

function chord(t) {
  const [beat, frac] = pos(t);
  const transpose = 0;
  const vol = sidechain(t);
  let mix = 0;
  const notes = [
    [0, 2, 4, 7],
    [0, 2, 4, 7],
    [0, 2, 4, 7],
    [0, 2, 4, 7],
    [-5, 1, 5, 10],
    [-5, 1, 5, 10.5], // whoa!
    [-6, 1, 5, 12],
    [5, frac * 6 % 1 < 0.5 ? 24 : 12],
    [-7, 0, 4, 7],
    [-7, 0, 4, 7],
    [-7, 0, 4, 7],
    [-7, 0, 4, 7],
    [-7, 0, 4, 7],
    [-7, 2, 4, 7],
    [-3, 2, 4, 5],
    [-2, 5],
  ][beat % 16];
  for (let i = 0; i < notes.length; i++) {
    const st = notes[i];
    const p = hz(st + transpose);
    mix += saw(tau * t * p, 3) * vol;
  }
  return mix;
}

function bass(t) {
  const [beat,frac] = pos(t*4);
  const i = beat % 16;
  const transpose = 0;
  const bassline = [-7,-7,-7,null, null, null, 0, 5, null, 0, 5 + Math.floor(frac*3)/3*2, 7, null, null, -12, null];
  if (bassline[i] === null) return 0;
  const p = hz(bassline[i] - 12 + transpose);
  const vol = 1;
  return (realsaw(t * p)*0.5 + Math.sin(tau*t*p)) * vol;
}

function delay(f, t) {
  let mix = 0;
  for (let i = 0; i < 7; i ++) {
    mix += Math.pow(0.6, i) * f(t + 64*spb - i * 0.2*spb);
  }
  return mix;
}

function shape(t) {
  return Math.tanh(2*t);
}

function kick(t) {
  const [beat,frac] = pos(t);
  const vol = beat % 2 === 0 ? 1 : 0.8;
  return shape(Math.sin(1 / ((frac+0.21) / 30))) * (1-frac) * vol;
}

function hat(t) {
  const [beat,frac] = pos(t*4);
  return Math.random(t) * Math.pow(1-frac, 4) * (beat%4/4);
}

function clap(t) {
  const [beat,frac] = pos(t);
  if (beat % 2 === 0) return 0;
  return (frac * 20 % 1 < 0.3 ? Math.pow(Math.sin(0.4 / ((frac+0.2) / 90)), 3) : Math.random() * 0.6) * Math.pow(1-frac, 8);
}

function drums(t) {
  return kick(t) + 0.2 * hat(t) + 0.8 * clap(t);
}

function dsp(t) {
  return 0.13 * drums(t) + 0.1 * delay(melody, t) + 0.03 * chord(t) + 0.03 * bass(t);
}