AudioContext playback without preloading

gistfile1.js

/*
Demo here: http://www.clicktorelease.com/tmp/fastload/
The MP3 file is 5.2MB
*/

/*
For some reason, probably because the spec has changed since the article 
"Getting Started with Web Audio API" in http://www.html5rocks.com/en/tutorials/webaudio/intro/
was published, the most common way of loading a file sound is something like:
*/

var oReq = new XMLHttpRequest();
oReq.open( 'GET', fileName, true);
oReq.responseType = 'arraybuffer';
oReq.onload = function (oEvent) {
  var arrayBuffer = oReq.response;
  // do arrayBuffery things, probably with AudioContext.context.decodeAudioData
};
oReq.send(null);

/*
Which forces the browser to download the file completely before starting decoding.
That's inconvenient because it's not necessary -AudioElement doesn't do that- and 
because it makes loading process unecessarily long.

So it turns out this works:
*/

var context = new AudioContext();
var a = document.createElement( 'audio' );
a.src = trackName;
a.play();
var audioSource = context.createMediaElementSource( a );
audioSource.connect( context.destination );

/*
The browser will start playing almost right away.
You can connect all the nodes you want, it all works the same

Tested with Chrome, Firefox and Safari OSX; Chrome and Firefox Android.
Haven't tried iOS.
*/