Click above to hear an audio version of this review, with musical selections. Audio produced by Derrick Stevens.

Sign o' the Times is the last R&B masterpiece before the influence of rap on the future of mainstream music became undeniable.

Freed from his backing band, the Revolution, Prince turned away from the virtuosic blast of the original Minneapolis Sound, and instead used his LinnDrum machine to create eerie skeletal arrangements that brought Prince's strength as a lyricist to the fore, like on the title track "Sign o' the Times."

When the song called for a full live band sound, Prince had no problem pulling together rockers like "I Could Never Take the Place of Your Man."

This headphones-required double album, full of live band chops and drum machine grooves, paved the way for artists like D'Angelo, Portishead, Miguel and many more, and when Questlove of the Roots says that Prince is, bar-none, the best drum programmer of all time, I imagine he must be thinking of numbers like "The Ballad of Dorothy Parker."

Sign o' the Times marks the rare moment when an artist had enough material and diversity of production to make a beginning-to-end masterpiece double album: one of the most elusive feats in all of pop music.