I know that I'm influenced by music - some of my fic is inspired by a song, or even just a particular line in a song, or, more rarely, by the feeling evoked by a song. I have music playing pretty much no matter what I'm doing - I love my mp3 player because it frees me from having to have a radio in the kitchen while I'm washing dishes - but I don't know that the music I have on influences the tone/mood of my writing as I'm writing. It's mostly there as background noise.

(Also, eee! Suzanne Vega! I do so love "Solitude Standing" and "Straight Lines", but also "The Queen and the Solider" and "The World Before Columbus".)