Depends on what I'm writing. If I'm writing a very specific scene with a very specific atmosphere, I may settle on certain songs to help my brain lock into that. But most of the time when I'm listening to music and writing, I'm actually trying to calm and relax myself down so I let out a solid stream. 

Most music I listen to for inspiration or just help my mood settle in tends to be before I start writing so I can start shifting through ides and concepts I like in a more casual manner.