I love music. Having music on in the background helps me get the creative juices flowing. They way I look at it, a persons musical choices says a lot about that person. Their personality comes through in the music that they like. Me, I'm a Concrete Blonde, Old NIN, EMO before it was EMO girl.
I can even map out particular characters personalities by the music I have playing as I'm writing them. I'll listen to their playlists over and over again, until I've got a good handle on their persona, the way they think. Olivia's Ipod playlist is a mix of BADII, Dave Navarro, and Tori Amos covers. Steven is a lot of 80's and 90's metal bands. My killer's playlist consists of tribal drums and chanting. There are a couple of characters that I havn't flushed out yet, so their playlists are pretty empty at the moment.