erasing artists in media library?
 

As I've been going through and looking over my media library to organize it, I notice that if an artist doesn't have any songs remaining, they still stay in the media library list of artists.. and I'm not really sure how to get rid of them. ie: if I have a song that might be by a couple artists.. let's say, Beyonce and 50 Cent (and that's how it's described in the ID3). When I change the tag from "Beyonce and 50 Cent" to "Beyonce", it moves to the right 'Artist' in the library.. but the old artist "Beyonce and 50 Cent" remains, and I'm not sure if there's any way to erase it.. does anybody know if this is possible and if so, how to do it?

Library Button > "Remove missing files from media library..."

thanks.. i thought i tried that (at least the right clicking option), but apparently not.. =\