musicforprogramming.net
Through years of trial and error - skipping around internet radio stations, playing our entire music collections on shuffle, or just hammering single albums on repeat, we have found that the most effective music to aid prolonged periods of intense concentration tends to have a mixture of the following qualities:
Drones Noise Fuzz Field recordings Vagueness (Hypnagogia) Textures without rhythm Minor complex chords Early music (Baroque, lute, harpsichord) Very few drums or vocals Synth arpeggios Awesome / daunting / foreboding Walls of reverb
Music possessing these qualities can often provide just the right amount of interest to occupy the parts of your brain that would otherwise be left free to wander and lead to distraction during your work.
Listen at http://musicforprogramming.net/.