When you have to study or get work done, what music (if any) do you put on to help you concentrate?
As a general rule, something classical in the rock fashion. Some of Mike Oldfield's stuff is good for this, and I can also put on some Jethro Tull (but not "Aqualung" or "Locomotive Breath"). Instrumental stuff works better for this than stuff with vocals.
Usually when I'm working, the music is background stuff, anyway.