Through years of trial and error — skipping around radio streams, playing entire collections on shuffle, or repeating certain tracks over and over — we have found that the most compelling music for sustained concentration tends to contain a mixture of the following:
Noise
Drones
Arpeggios
Atmospheres
Field Recordings
Arrhythmic Textures
Vagueness (Hypnagogia)
Microtones / Dissonance
Detail / Finery / Patterns
Awesome / Daunting / Foreboding
Vast / Transcendental / Meditative
Music possessing the above qualities can provide just the right amount of cognitive load to engage the parts of your mind that would otherwise be left free to wander and lead to distraction.