When you add writing to that, it's not always a good mix. If the music has words, I may start typing them into my story--and I don't mean in natural ways.
Once upon a time, there was deck the halls a princess. . .
Usually, though, I just stop writing and start singing.
If it's an Irish tune, I'll dance to it--or be so distracted by wanting to dance that I won't write. Okay, this applies to any music with a beat.
There is one exception I've found to both these "problems": what I call coffee shop music. (Think Regina Spektor, Lenka, &c.) It's just soothing enough to keep me motivated.
When that fails, and I start singing, dancing, or both, it's time to switch to classical. Or jazz, but when my focus level gets to this point, swing dancing is tempting even without a partner!
What is on your writing playlist?