Masters of their appointed tasks, rapper Rakim and DJ Eric B. are also formal innovators. They both can riff and improvise like jazzmen, spinning endless variations on basic themes and playing off each other's moves with chilly intuition. The resulting music is as stark, complex and edgy as Rakim's stone-cold stare on the album cover.

In the course of his freestyle rhyming, Rakim does a lot more than just pump himself up. He touches on his solid Muslim faith ("No Omega") and delivers canny social observations ("In the Ghetto"), smoothly speaking his piece and then moving on. Compared with the right-on sermonizing and bandwagon conformity proffered by his peers, Rakim's probing vocabulary and individualist's stance present a model of subtlety. He even gives listeners credit for having an idea or two of their own!

Eric B. mixes beats and snatches of melody with a be-bop drummer's sure, steadily swinging hand; he's the Max Roach of the twin turntables. Listen to how he echoes and comments on Rakim's lines throughout "Keep 'Em Eager to Listen" without ever stopping the groove. And on "Untouchables" these two take hip-hop straight to the astral plane. Whether scratching up the late-Sixties sound of freedom jazz or matching a walking acoustic bass and a wailing trumpet to the call of the funky drummer, this bold attempt at cross-generational fusion says more about the Afro-American cultural continuum than a truckload of medallions and dashikis. A lot of rappers talk about "dropping science" these days; Eric B. and Rakim just do it.