It begins with the insistent drip-drop of a sequencer and ends with some old school R&B. In between, the artist who was still calling himself Prince unfurls an encyclopedia of moods, genres, and grooves. Widely heralded as a groundbreaker in 1987, when it was released, some of the music in oh-so-'80s synths sounds a bit dated. Yet this two-CD set is clearly the sound of a performer at the height of his power. On songs like the title track, "If I Was Your Girlfriend," and the thunderous "The Cross," Prince proves why the hype was justified.