Sound question

Howdy Folks!!

I have a question about controlling sound in flash. I keep hearing it is a good idea to assign your sound objects to separate movieclip containers in order to control them separately…but I was doing some testing, and I noticed that I seemed to be able to control multiple sound objects independently with all of them assigned to one movieclip container. Why might this be?

 
this.createEmptyMovieClip("mcSoundHolder1", this.getNextHighestDepth());
var sndAudio1:Sound = new Sound(mcSoundHolder1);
var sndAudio2:Sound = new Sound(mcSoundHolder1);
sndAudio1.loadSound("tracks/primo1.mp3", false);
sndAudio1.onLoad = function(bSuccess):Void {
 if(bSuccess){
  trace("sound1 loaded successfully");
  this.start();
 }
};
sndAudio2.loadSound("tracks/primo3.mp3", false);
sndAudio2.onLoad = function(bSuccess):Void {
 if(bSuccess){
  trace("sound2 loaded successfully");
  this.start();
 }
};
sndAudio1.setVolume(100);  // seems to work ok
sndAudio2.setVolume(20);  // seems to work ok
mcStop1.onRelease = function():Void {
 sndAudio1.stop();  // stops 1
};
mcStop2.onRelease = function():Void {
 sndAudio2.stop();  // stops 2
};

Also, while I am having an easy enough time controlling sound objects independently (as far as start, stop, setVolume, setPan, etc.)…I haven’t been able to “skip” from one track to another. How might one do this? An associative array somehow to create the order of the tracks, or some other technique?