OutKast’s musical prosperity is no accident. It’s the product of a major black-owned label giving rare creative freedom and financial support to talented black artists. With today’s rap producers pummeling themselves over strict sampling laws, the rousing and seemingly spontaneous harmonica solo on Aquemini’s first single, “Rosa Parks,” must have made them want to die. On “Da Art of Storytellin’ (Part 2),” Andre and Big Boi’s disturbing vocals are harshly distorted, and they end suddenly with the gothic singing of “All’s well, nothing’s well” that is just plain spooky. Big Boi issues a dare: “Makin’ them think Hip Hop is dead/Exhume the body if you ain’t scared” over neoclassical strings and piano on “Chonkyfire,” proving that OutKast will fearlessly try anything. Their ambition forces their guests to match their pace: On “Synthesizer,” a mellowed-out George Clinton raps in high-tech fashion over a track that issurprisinglynot another rehash of ancient P-Funk. Firebrand Raekwon sizzles on the upbeat “Skew It on the Bar-B,” while Erykah Baduless pretentious than usualgives her poetic thoughts on the music biz on “Liberation.” Now, if only the Artist would sign Q-Tip to Paisley Park.