"They" did provide for multiple genres in the ID3v2 tag format, but having multiple artists/genres isn't directly supported by the player/emplode software. This is definitely on the wish list, though.

Soup views are also in the works, but as you may have noticed, the guys are real busy these days, so I wouldn't hold my breath for it. No real workaround except for copying your songs into multiple "genre playlists" or whatever. It's a crappy workaround, but hopefully some day the Cambridge guys will have some free time to work on the player again.