If you want it to play on forumhome, you can put it into the header as a variable defined in the phpheadinclude...maybe using the request url to compare it. $REQUEST_URI seems to be a variable in php, I have used it in the past.
to play only on forumhome, in phphead include you may do something like...
PHP Code:
if ($REQUEST_URI=="/forumdir/index.php"){
$playmusic="<Script in here>";
}else{
$playmusic="";
then in header put where the play music script would go $playmusic