On the tagging of music

So I'm curious. Do we not live in an age of tagging? Do we not tag everything, from our goals to our journal entries to our finances? I know that Last.fm and other similar web interfaces have brought the idea of tagging to music, but what I want to know is... Why is that only on the web? Wouldn't it be awesome to have a media player that did that?

I would happily donate my money to a media player that will:

• Allow me to tag my music


• Put multiple tags on each MP3


• Sort and filter by tags (way better than playlists, imho)


• Work with my iPod and maybe ripmy iTunes downloaded music

I'd like to think this would be a popular idea, so I can't imagine why it's not out there already. Is that really hard? It seems like it wouldn't be that big a deal compared to the really wacky media player interfaces I've seen.