How to stop site's music when opening link in new window?

1

I have a client who has a link, in a dynamically-loaded .txt file within a scroller in flash, and it is a youtube link with audio, that opens in a new window. He really wants his site’s music to stop once this link is clicked. Anyone out there know of the best, least complicated way I can get this done?? I mainly just know Flash and AS 2.0