iTunes/Mp3-Player and actual multi-tagging of MP3s

Question

I search for a software to allow multi-tagging. Meaning, i want to add more than one genre to a song/album to be able to easily access specific songs i.e. ("female singer, jazz" or "duet, jazz") which i can not realy do by choosing just one genre.

Is there an option to do this with iTunes? If not, is there a player able to do this? Maybe even with pandora/last.fm/musicbrains interface so i don't even have to tag all the songs myself?