[niftich]

For this purpose, I too listen to music mostly without vocals, or if vocals are present, they are the simplistic, melodic sort found in the likes of vocal trance.

Genres like trance help me focus because of a typical track's long duration, repetitive structure, and grandiose buildups.

When I need a little bit more stimulation, I switch to a less regular, more punchy EDM genres like electro house, or something with dubstep-inspired drops.