<button>
  Play music
</button>
<script>
// create web audio api context
var audioCtx = new(window.AudioContext || window.webkitAudioContext)();
function playNote(frequency, duration) {
  // create Oscillator node
  var oscillator = audioCtx.createOscillator();
  oscillator.type = 'square';
  oscillator.frequency.value = frequency; // value in hertz
  oscillator.connect(audioCtx.destination);
  oscillator.start();
  setTimeout(
    function() {
      oscillator.stop();
      playMelody();
    }, duration);
}
function playMelody() {
  if (notes.length > 0) {
    note = notes.pop();
    playNote(note[0], 1000 * 256 / (note[1] * tempo));
  }
}
notes = [
  [659, 4],
  [659, 4],
  [659, 4],
  [523, 8],
  [0, 16],
  [783, 16],
  [659, 4],
  [523, 8],
  [0, 16],
  [783, 16],
  [659, 4],
  [0, 4],
  [987, 4],
  [987, 4],
  [987, 4],
  [1046, 8],
  [0, 16],
  [783, 16],
  [622, 4],
  [523, 8],
  [0, 16],
  [783, 16],
  [659, 4]
];
notes.reverse();
tempo = 100;
playMelody();
</script>