Anyway, I've had this perl module I wrote awhile back for object persistence of song metadata. Yeah, it's not a general purpose persistence module, but it could be without much hacking. I think it's a pretty kick ass module, you can easily search for songs, artists, genres, etc etc without ever knowing a single line of SQL. But if you do know SQL, it inherits/extends from perl's DBI, so you've got all that power available too.
So I've put together some UML diagrams for AudioDBI cause I think AudioDBI is the cat's ass. And this is my journal so I can pitch the bitch if I like. So if you're a perl d00d, and have an itch for messing with song metadata within your program, or more generally, if you need object persistence, check it out.