I've experimented with different types of music while working/coding, and I've found the perfect thing that works well for me, which is soundtracks from RTS games. They're instrumental, vaguely electronic, and specifically designed to fade into the background and create a general sense of urgency and focus.
If you are a big Starcraft player for example, playing the background music from Starcraft can create a sort of Pavlovian Response, telling your brain "You are sitting at a computer carrying out a difficult task which takes a good deal of focus and mental exertion. This activity is fun and rewarding, and it is urgent that you do it as well and as quickly as possible."
If you are a big Starcraft player for example, playing the background music from Starcraft can create a sort of Pavlovian Response, telling your brain "You are sitting at a computer carrying out a difficult task which takes a good deal of focus and mental exertion. This activity is fun and rewarding, and it is urgent that you do it as well and as quickly as possible."
Give it a try.
tl;dr Soundtracks from RTS games