ActionScript 3.0 :: Swapping The Sound Files?

I am working on a Flash / AS3 project which has several audio tracks and starts off with an intro track. When the user clicks a button a window opens and the audio track changes, the new audio track continuously loops until the user closes the window. When the window is closed the audio track switches to a default audio track which is similar to the intro track. The problem I am having is that when the user clicks on the button and the window opens, the audio track plays as expected, but when it reaches the end, it doesn't loop, instead the intro track starts to play instead (and loop I assume).

Here is the code I am working with:

Code:
package {
import flash.events.Event;
import flash.events.EventDispatcher;
import flash.events.MouseEvent;
import flash.media.Sound;

[code]....

I included trace statements to track what the value of "music" is doing. It appears that when the function repeat() occurs, "music" always seems to default to the intro music "audio/track-intro.mp3".