OK, so I couldn't remember the rules of FID creation... :-) The point remains the same - you don't need much space to encode the information you want to store. I don't think, in retrospect, that you'd need more than those 5 (four explicit, one implicit) levels of preference stored. But perhaps other things could be stored in the remaining unused bits - how much you liked the song, for instance.

As empeg seem to have the concept of marking a song for later attention somewhere in their wish list, I won't say it again...

Save the whales. Feed the hungry. Free the mallocs.