It isn’t expedience, it isn’t desperation, it isn’t eccentricity of vision per se: Whatever compels Prince to continue expounding on his idea of a spirito-sexual musical revolution remains a mystery all these records away from his greatest, most populist work. He’s digging in his high heels harder than ever on the busy, portentous The Rainbow Children. It cops jazz forms without swinging, gets James Brownishly funky minus the urgency, and offers church interludes that are too mystical to carry earthly convention. Laid out as a series of “chapters,” the tracks provide a text for the everywhereness of God and find him mostly in the bedroom. Heavily processed vocal intros provide a biblical weight to each number, as do Gnostic references to the Banished Ones, ambiguous numerology, ambiguous vegetarianism and his talk of “displaced bloodlines.” But this is Prince, and if the laid-back jazz funk doesn’t interest him, he can always get rowdy with the ladies. His admonishing tone and dubious history take a back seat to the fine, sexy stuff — the simple ballad “She Loves Me 4 Me,” the grooving “Mellow” and “1+1+1=3.” But it’s a long trudge across the desert to this heady water, especially with Freak-in-the-Pulpit leading the way, waving his synthesizer of holy justice.