We are now winding down the anniversary of hiphop's 30th year of existence as a populist art form. Testimonials and televised tributes have been airing almost daily, thanks to Viacom and the like. As those digitized hiphop shout-outs get packed back into their binary folders, however, some among us have been so gauche as to ask, What the heck are we celebrating exactly? A right and proper question, that one is, mate. One to which my best answer has been: Nothing less, my man, than the marriage of heaven and hell, of New World African ingenuity and that trick of...