I'm always interested to hear about other people's writing processes :3 Way back when I didn't RP and just...was doing original writing and fanfiction I had a playlist of just "Writing Music" which was about 80% of what I owned. Needless to say I wasn't very creative with naming.
What I find though, as I'm strongly influenced by what I hear, is that the music I listen to tends to affect the tone of what I'm writing. If I write a fight scene and a Disney song comes on? It tends to end in crack and so on.