vibrato.js

/*
var freq = [5, 8, 1, 9, 9,   5,   8,   1,   8, 5, 1]
var bass = [1, 0.1, 0.1, 1, 1.3, 1.6, 1.3, 1.5, 2, 1.6]

function note(n) {
  return 440*Math.pow(2, (n-49)/12.0)
}

function sin(f, t) {
  return Math.sin(2 * Math.PI * f * t)
}

function dsp(t) {
  var fi = Math.floor(t*3) % freq.length
  var s = 0.0
  s += sin(note(48+freq[fi]), t)

  var r = 0.0
  for (var i = 0; i < 4; i++) {
    r += sin(.5*220*freq[(fi+i)%freq.length], t)
  }

  var b = 0.0
  var bi = Math.floor(t*3*2) % bass.length
  b += sin(bass[bi]*100, t)

  return (
    s*0.2
  + r*.02
  + b*0.4
  )
}
*/

var freq = [5, 8, 1, 9, 9,   5,   8,   1,   8, 5, 1]
var bass = [1, 0.1, 0.1, 1, 1.3, 1.6, 1.3, 1.5, 2, 1.6]

function note(n) {
  return 440*Math.pow(2, (n-49)/12.0)
}

function sin(f, t) {
  return Math.sin(2 * Math.PI * f * t)
}

function Oscillator(type, size, alias){
  if (!(this instanceof Oscillator)) return new Oscillator(type, size, alias);
  this.pos = 0;
  this.size = size || sampleRate;
  this.coeff = this.size / sampleRate;
  this.table = new Float32Array(this.size);
  this.alias = alias === false ? false : true;
  this.build(type);
}

Oscillator.prototype.build = function(type){
  switch (type) {
    case 'sin':
      var scale = 2 * Math.PI / this.size;
      for (var i = 0; i < this.size; i++) {
        this.table[i] = Math.sin(i * scale);
      }
      break;

    case 'saw':
      for (var i = 0; i < this.size; i++) {
        var x = (i / this.size);
        this.table[i] = +2.0 * (x - Math.round(x));
      }
      break;

    case 'ramp':
      for (var i = 0; i < this.size; i++) {
        var x = (i / this.size);
        this.table[i] = -2.0 * (x - Math.round(x));
      }
      break;

    case 'tri':
      for (var i = 0; i < this.size; i++) {
        var x = (i / this.size) - 0.25;
        this.table[i] = 1.0 - 4.0 * Math.abs(Math.round(x) - x);
      }
      break;

    case 'sqr':
      var half = this.size / 2;
      for (var i = 0; i < this.size; i++) {
        this.table[i] = i < half ? +1 : -1;
      }
      break;
  }
};

Oscillator.prototype.play = function(freq){
  this.pos += freq * this.coeff;
  if (this.pos >= this.size) this.pos -= this.size;
  this.index = this.pos | 0;
  if (!this.alias) return this.table[this.index];
  this.alpha = this.pos - this.index;
  this.next = this.table[this.index == this.size - 1 ? 0 : this.index + 1];
  this.curr = this.table[this.index];
  return this.curr + (this.next - this.curr) * this.alpha;
};

var sin_s = Oscillator('sin');
var sin_r = Oscillator('sin');
var sin_b = Oscillator('sin');

function dsp(t) {
  var vibrato = sin(10, t) * 8;
  var fi = Math.floor(t*3) % freq.length
  var s = 0.0
  s += sin_s.play(note(48+freq[fi]) + vibrato)

  var r = 0.0
  for (var i = 0; i < 4; i++) {
    r += sin_r.play(.5*220*freq[(fi+i)%freq.length] + vibrato)
  }

  var b = 0.0
  var bi = Math.floor(t*3*2) % bass.length
  b += sin_b.play(bass[bi]*100 + vibrato)

  return (
    s*0.2
  + r*.02
  + b*0.4
  )
}