With his wide-ranging collaborations, Avicii left his signature all over pop music. His knack for killer chords drives Coldplay's “Hymn for the Weekend”; his bouncy synth leads lend David Guetta's “Lovers on the Sun” its playful edge. The Swedish producer's remixes are no less pivotal: Reworking Daft Punk's “Derezzed,” he keeps the spirit of the original while giving it his unmistakable, irresistible melodic polish.