s = new Sound();
s.attachSound("aaaa");
s.start(0,1);

s :Sound= new Sound();
s.attachSound("aaaa");   // 不能用=
s.start(0,1);

var song_sound:Sound = new Sound();
song_sound.attachSound("aaaa");
S.onRelease = function() {
    song_sound.start();
};
SS.onRelease = function() {
    song_sound.stop();
};