With sanctimonious haters wagging fingers from both sides of the populist/avant-garde divide, the underground hip-hop world can be ruthless in its contradictions. While progressive anomalies often reach the top of the charts, reflexively marginal artists are left with two unappealing options: Keep it real and get grilled as tired traditionalists, or stray off course and risk betraying hip-hop's communal ambitions. Anti-Pop Consortium leaned emphatically toward the latter course on 2000's Tragic Epilogue, a striking debut that raised the rap stakes with dizzying production and hyper-abstruse rhymes. The album made tiny waves in New York and overseas, but detractors wrote off Anti-Pop Consortium as a group of cerebral eggheads. The taut and decidedly less clinical new Arrhythmia is a well-aimed shot at the doubters. "Bubblz" boasts more bounce and snap in three minutes than all of Epilogue, rolling conga taps and sub-bass massage over pop-and-lock beats. Elsewhere, "Ping Pong" is a minimal banger built from sampled table-tennis sounds. Lyrically, Anti-Pop Consortium lays down the hip-hop equivalent of the New York Times' Sunday crossword puzzle. "Dead In Motion" rubs all of the group's touchstones together: Beans' sing-songy dancehall delivery, M. Sayyid's swaggering toughness, and a contemplative turn by Priest, who rides the line "toxins start to leak out of your skin / murderous carcinogens hemorrhaging" into a reference to old-school wrestling star Paul Orndorff. In spite of a languorous middle section and occasional prog-rock indulgences (an operatic interlude on "Mega" sounds suspiciously like Queen), Arrhythmia offers a playful lesson in hip-hop's most erudite and engaging extremes. The album's release on abstract electronic label Warp reveals Anti-Pop Consortium's long-held science-fiction concerns, but the group's ability "to write trifling poems on ohms" blurs fantasy and reality in newly convincing ways.