Fade out MP3 individually

Question

Tie this code to a button, if I repetitive press as  fast as I can, an error exception would appear in the application. I  found that it would not throw an error if I stop the sound when it  completely fade out. However, I wish the fade out function could stop  the sound individually, not stop o1_1 together. Similar to a piano keyboard, how do I do that?
private var s1_1:Sound = new Sound();
private var o1_1:SoundChannel = new SoundChannel();
private static const a1_1:String = "1.mp3";
private function p1_1():void{
s1_1 = new Sound();
s1_1.load(new URLRequest(a1_1));
o1_1=s1_1.play();
private function fade1_1():void{
TweenMax.to(o1_1, .35, {volume:0, onComplete:stop1_1});
    private function stop1_1():void {
//if I add, this code would only stop the sound altogether rather than individual. I wish to have each of the instance stop itself.
    o1_1.stop();
My error exception in Flex builder 3 using SDK 3.5 and AIR 2.0:
[SWF] snd.swf - 1,022,361 bytes after decompression
TypeError: Error #1009: Cannot access a property or method of a null object reference.
     at snd/st1_1()[...snd.mxml:44]
     at snd/___snd_Button1_mouseUp()[...snd.mxml:67]

Answer 1

the way I do it, or what I think you're trying to do, is go to the last frame you want to fade out, in your case the last frame, go to edit and select 'create still image' or something to that effect, and in the raw footage bank a 5second still image should apear of that frame. then click and drag it, go to the transition section and select the type of fade out you wish to use. Hope that helped.