As a bit of background to this question, I have over 4000 mp3s in my main iTunes library and they're all tagged as about four thousand different genres. I want to retag them so that they're all one of, say, ten different genres, which will make it much easier to sort them with smart playlists. I'm just having problems thinking up generic enough genres for them. I mean - there's "rock", but what does that include? What genres would you use to tag the library? Keep in mind that I have everything in this from death metal to celtic to opera to disney to mainstream rock to jazz and so on. I don't think I have one style of music that isn't represented in this monstrosity.
So - genres. What do you think are the core ones?