When I was in high school, my math teacher would play Mozart during tests, claiming it would help us. It would drive me crazy, and I doubt that my grades improved as a result of the distraction.
For what it's worth, I have a BMus in Piano Performance. I love music... but never as "background noise"!
I'd be curious to know if there are any serious musicians here who can concentrate on writing code or any other similarly mentally-intensive task while listening to music.