It may seem cliche fancy but I can go for hours with smooth jazz sax in the background. no lyrics help me focus on the task at hand while my mind can be in a relaxing/stimulating environment.

By this I mean most jazz music is slow-tempered and chill-out while also offering impressive musical talent for lead instruments (sax solos, piano, strings...). This is just what works for me - a buddy of mine swears on the Kingdom Hearts soundtrack.