What a cool thread. Quite a bit of my writing was done with great tunes in the background.
The tongue in cheek, descriptive parts, when my mind needs a bit of shock treatment, Pink, Red Hot Chili Peppers, ZZ Top, etc. come to the rescue.
The darker parts are hard to write but groups like Portishead usually work. But, I like to share music with other writers...it does help bring the creative parts to the surface.
Also, I write naked, with my collar on.