[msbmsb]

Anything that I already know very well (and like, of course). What that is will depend on the day/mood.

The main thing is that I find I work better with music already known over silence or new music. My brain can kind of just go along with it without any extra work since the patterns are familiar and it seems to help thought flow.

There are times when I prefer no music though, if it's involved research or something I really need to think over or internally debate.