If you put class=”htrack” on some of the mp3 links, only mp3 links with class=”htrack” will be in the playlist.

A bit more info on that is here: http://yahoomediaplayer.wikia.com/index.php?title=How_to_link&oldid=3750

About JS interactions, see Paul Irish’s hacks in his blog at aurgasm.us. Otherwise I’d ask the mailing list about that…