I always listen to music while writing, but I do not listen to set mood. In fact, I don't
WANT the music I'm listening to influencing my mood.
Rather, I want thought-cleansing music that helps me focus on my work. Something that washes out other distractions and zones me out. No singing. No lyrics. Usually it means something calming and ambient, such as Brian Eno or Windy & Carl or Labradford, or possibly mid-period Miles Davis if I'd like something more upbeat. Often it's aggressively room-filling drone/ambient music, such as my own
m2 project, which I record in part because it relaxes me. (It's not for everyone. I know someone who listens before he goes diving because it sort of cleans out his mind. To other people it's unbearable.)
Orchestral music is also a frequent choice.
Like I said, I don't want something to influence my mood, I want something to fill up the room and cancel out everything but me and the keyboard.