3 композиции проиграются друг за другом после запуска мувика:

Код:
music1 = new Sound();
music1.loadSound("Shania1.mp3");
music2 = new Sound();
music2.loadSound("Cranberries1.mp3");
music3 = new Sound();
music3.loadSound("Cranberries2.mp3");
music1.onLoad = function(){music1.start();}
music1.onSoundComplete = function(){music2.start();}
music2.onSoundComplete = function(){music3.start();}