Mp3 player with volume slider using Actionscript 3

//attatch/import the music file.
var musicPiece:Sound = new Sound(new URLRequest _ 
("http://blog.0tutor.com/JeffWofford_Trouble.mp3"));

// Make a sound channel to change sound configurations.
var mySoundChannel:SoundChannel;

// This variable is checking if the music is playing
var isPlaying:Boolean = false;

// to remember the position of the music playing when we pause, _ 
to start at the same place


var pos:Number = 0;

// First button we will make is a play button, add an eventlistener.
play_btn.addEventListener(MouseEvent.CLICK, play_);

function play_(event:Event):void {
//Check if the music is NOT playing, then make it start.
if (!isPlaying) {
mySoundChannel = musicPiece.play(pos);
isPlaying = true;
}
}

// The pause button, here we will use the pos variable we made earlier.
pause_btn.addEventListener(MouseEvent.CLICK, pause_);

function pause_(event:Event):void {
// if the music is player, save the current time and stop the playing.
if (isPlaying) {
pos = mySoundChannel.position;
mySoundChannel.stop();
isPlaying = false;
}
}

// Now the final button is the stop button, allmost thet same as pause
stop_btn.addEventListener(MouseEvent.CLICK, stop_);

function stop_(event:Event):void {
// First we check if there is anything to stop then make it stop, and reset the pos variable to 0 (start time)
if (mySoundChannel != null) {
mySoundChannel.stop();
pos = 0;
isPlaying = false;
}
}

// this is a bit complicated, but I will try to explain anyway.
// first we make a rectangle and set its width to 100.
var rectangle:Rectangle = new Rectangle(0,0,100,0);

// then we need a varible to check if the handle is being dragged.
var dragging:Boolean = false;

// the eventlistener for startdragging
volume_mc.mySlider_mc.addEventListener(MouseEvent.MOUSE_DOWN, startDragging);
function startDragging(event:Event):void {

// here we tell flash the margin on where it should be able to drag, (remember 100 pixels back and forth)
volume_mc.mySlider_mc.startDrag(false,rectangle);
dragging = true;

// This is very important, an eventlistener so we can change the volume, not only make it look good.
volume_mc.mySlider_mc.addEventListener(Event.ENTER_FRAME, adjustVolume);
}

// well here is the adjust volume function, its not that complicated
function adjustVolume(event:Event):void {

// we make a variable to calculate the volume from the slider handle position and divide it by 100
var myVol:Number = volume_mc.mySlider_mc.x / 100;
// then we set it with the mySoundTransform
var mySoundTransform:SoundTransform = new SoundTransform(myVol);
if (mySoundChannel != null) {
mySoundChannel.soundTransform = mySoundTransform;
}
}

// and of cause the stop draggin function, I dont feel the need to explain it.
stage.addEventListener(MouseEvent.MOUSE_UP, stopDragging);
function stopDragging(event:Event):void {
if (dragging) {
dragging = false;
volume_mc.mySlider_mc.stopDrag();
}
}