gistfile1.js

function say(phrase, language) {
    var audio = ...
    return audio.play()
}   

function Audio(...) {
}

Audio.prototype.play = function () {
    var def = new $.Deferred()
    var player = new Player();
    player.onFinsish(function () { def.resolve() });
    player.play();
    return def
}

say("hello", "en").then(doTheNextThis).fail(errorhandler);