Obfusc, featured on the Monument Valley soundtrack, has made its albums available at no minimum donation (i.e. free) on Bandcamp.
As a connoisseur of non-vocal, limited-distraction music, I highly recommend it. Probably a touch to electronic for some, I find it hits a sweet spot between soporific ambience and brain-flaying electronica.
Also highly recommended is the iOS game that introduced me to the artist: Monument Valley—an Escheresque puzzle game with amazing attention to quality and detail.