The polyrhythmic spectacle unleashed by Femi Kuti and the Positive Force is peerless. The proud torchbearer of Afrobeat's musical and political legacy, Kuti brings a massive band: costumed dancers, horn players, a wire-tight rhythm section, and his own half-braggadocio/half-polemic vocals. The sound is bigger than big, funkier than funky, infectious and totally unstoppable. (Showbox, 1426 First Ave, 628-3151. 8 pm, $25 adv/$28 DOS, 21+.)