iTunes really needs some kind of actual tagging feature. It has smart playlists, which let you choose songs by setting filters that find music for you based on song info. But all you have to work with are the fields Apple gives you, so doing anything more custom than filtering by those means you have to cannibalize an existing field....
(Aw, heck....)
Also...KAITO.
http://www.mikufan.com/wp-content/uploads/2012/10/ca518279d33e13b9b8f90e62aac12320.jpg
I've always liked these Inception-esque sorts of things (i.e., Miku, listening to music), and since I've been working with my music library, the image struck me.