Classical music is the only music I can listen to when revising. It is the only genre that can relax you, have interesting moments, but not disturb you too much. All other forms are too obtrusive for revising I think.

Classical music, in general, is so complex (even Vivaldi) it draws off my mind into the music.
If I really need concentration, I listen to silence. Or some drone or something...

Depends on what you're doing I suppose. I like hardcore rave when playing blitz chess.
But, even then, when I need to focus, the music goes down.