Always while I work (not just programming):
classical music. a. It generally has no lyrics (apart from some Latin or German etc.) Which is good because when you're writing words or code you it's irritating to have lyrics.
b. Very calming. Work can be stressful and the music helps.
c. A good understanding of classical music (you'll get one by listening to it a lot) is great to have. Employers like it because it makes you seem "cultural (don't like the word tbh)", and there's an long and interesting history to the subject.
I like a lot of music, but Classical is definetley the most expressive. And when I say classical I mean a lot of things. Film music counts, I had the Shawshank Redemption soundtrack on the other day. Great track called Ziheutanajo or something like that..
Also Fantasia in D minor by Mozart.