This summit between two Young Turks of the blues harmonica should be one of the more musically and aesthetically intriguing shows we've had for awhile. Sugar Blue and Billy Branch are virtuosos, intent on keeping the blues relevant in the contemporary era. Branch, a self-proclaimed "Son of the Blues," explores eagerly but cautiously into areas not previously charted by his mentors (Big Walter, Carey Bell, et al.). Despite his mastery of his instrument, he often relies on his band's diverse musical influences to provide the bridge between traditional and the contemporary. Sugar Blue, on the other hand, approaches blues like James Joyce approached prose--with icon-shattering audacity and dazzling technique, he virtually deconstructs the entire blues vocabulary and then attempts to piece together a new, blues-based language from the smoldering fragments of the old. These two players push the harmonica to its limits as both a repository of tradition and a harbinger of new ideas, representing vastly disparate philosophies on how to carry the blues torch into the future. Whether they can jell their differences into a coherent night's music is open to question. The attempt, though, could be ear-bending. Tonight and Saturday, B.L.U.E.S. Etcetera, 1124 W. Belmont; 525-8989.