Lots of Vocaloids actually. I have a long list of songs from up beat to melancholy depending on the mood of the piece I'm working on. I find the music inspirational since it is all fan generated and there are some very cute music videos that I'll watch to get myself started in the day. I know, not everyone likes the sound of them, takes time to get used to and find the right producers.
I need music because my wife tends to be playing video games and chatting on Voice chat with our friends just across the table so I need to block i tall out or I'll be distracted by what they are doing and want to play instead of working...