introduction-to-web-audio-api.js

var actx = new AudioContext();
var sound = actx.createBufferSource();

var req = new XMLHttpRequest();
var audioFile = 'https://dl.dropboxusercontent.com/u/87705298/136351__djmastah__requiem-3.mp3';

req.open('GET', audioFile, true); req.responseType = 'arraybuffer';
req.onload = function() {
  actx.decodeAudioData(req.response, function(buffer) {
    sound.buffer = buffer;
    sound.connect(actx.destination);
    sound.start();
  });
};

req.send();