Many people think of Eddie Harris and Les McCann as the jazz equivalent of Mutt and Jeff, and the analogy concerns more than their appearance. (Harris is relatively trim, McCann extravagantly rotund.) McCann came on the scene as a blues-drenched pianist/vocalist, soulful, entertaining, and not too much of a challenge–a description that holds true today as well. Harris started with a majestic tenor-sax virtuosity that often gets lost in his street-smart imagery and went on to experiment with the hardware, mastering various electronic enhancements and inventing the hybrid “reed trumpet” in the 60s; in the 70s he confounded listeners by producing an entire album of X-rated onstage monologues. But what Harris and McCann have in common is rhythm, specifically their complementary approaches to the funky rhythmic patterns that began to emerge in the 50s. McCann burrows into these rhythms, laying the broad beams of the beat as a foundation; Harris uses his feathery tone and insinuating grace notes to provide the almost refined, certainly exhilarating cornices. Separately these approaches carry plenty of tradition: McCann upholds the blues piano greats of jazz antiquity, while the infectious shuffle that Harris designed in the 60s paved the way for house music. Combined, they create the powerful and infectious stomp at the heart of “Compared to What,” their signature hit of 1969 (and the prime motivation for their occasional reunions). Friday through Sunday, Joe Segal’s Jazz Showcase, Blackstone Hotel, 636 S. Michigan; 427-4846.