Consider "Backseat Freestyle" from last year's masterful good kid, m.A.A.d city. In three and a half minutes, Kendrick Lamar moves from a nerdy yammerer conflating his dreams with MLK's, to an alpha male MC all about his dick, to, for a little while there, some futuristic hybrid of Lil Wayne and Eminem, all croaks, and grunts and cries. The song wobbles because it's so ambitious but it never falls down and the chance for it all to crumble or reach head-spinning heights is what gives the vocal tour de force its power. Just as frequently though, good kid is marked by Lamar's decision to impose limits on his delivery. There's a sense that this always thinking, constantly reevaluating young man, who can channel Nas's street poet focus or say, Project Blowed's rambling head-in-the-clouds words-for-words-sake expressionism, has an unlimited number of sides and he's reining it in for the sake of cohesion. He's an indulgent rapper, but he's also a masterful editor who knows his strengths. That's rare right now. good kid demanded his most self-serious rhymes. "Backseat Freestyle" was the one chance to go off. Appropriately, just as good kid was recognized as a mature and wizened masterpiece, and Kendrick rap's new savior, he proved he could also get ignorant with his big deal buddies on A$AP Rocky's radio hit, "Fuckin' Problem." That's amazing. B.S.