Buffer Source (playback wav file)

    window.document.onkeyup = function(evt){
    var src = ctx.createBufferSource();
    if (evt.keyCode == 13)
        src.buffer = tan;       // return key
    else
        src.buffer = kacha;     // the other keys
    src.connect(ctx.destination);
    src.start(0);
    return false;
}