Well, I do find that when I want to sleep during the day, any classic rock (ie Metallica, Deep Purple, Maiden etc) is so familiar that I don't need to listen to it and it soothes me off to sleep, but tracks like "Boiler" by Limp Bizkit or "The Nobodies" by Marilyn Manson just seem to put me in a really hyper mood - I end up grinning if I turn "Boiler" up too high.

Spoken stuff puts me straight to sleep if I'm already tired, which is one of my many reasons for disliking radio..

I have been finding that a good bit of Bartok or Kachachurian keeps me alert, but I don't have enough classical stuff on my empeg yet.

Of course with enough Red Bull, I would be awake no matter what music was playing - I would just be driving far too quickly!