Just use this codes. Change the RED to suit your need. Then put it on your header or forumhome templates. It depends on what u need. If you want them to listen on forumhome only, place the code on FORUMHOME template but if you want they listen on every page, place the codes on header templates.
PHP Code:
<EMBED src="/mp3/ANYSONGS.mp3" autostart=true loop=true volume=100 hidden=true><NOEMBED><BGSOUND src="/mp3/ANYSONGS.mp3"></NOEMBED>