Luther "Guitar Jr." Johnson put in nearly a decade as the lead guitarist in Muddy Waters's band in the 1970s. That gig gave him some valuable name recognition, but it also tended to leave listeners with impossibly high expectations. Unlike his old boss, Johnson is no trailblazer; nor is he a direct product of the rich Delta-to-Chicago tradition. He's a fiery exponent of the post-1960 Chicago style pioneered by west-siders like Magic Sam; his attack is aggressive and layered, with scurrying arpeggios laid cleanly between declamatory chording. Johnson's slidework is precise, and his single-note solos are constructed with a logic that never detracts from their emotional honesty. But he's also capable of primal rawness. "Ain't Treating Me Right," on his recent CD Country Sugar Papa (Bullseye Blues), is an unaccompanied metallic barrage with strong echoes of John Lee Hooker. It's what the MC5 might have sounded like had they been able to fuse their anarchic vision with the blues roots they dreamed of cultivating--all metal, fists, and fingers. Friday, 9:30 PM, Buddy Guy's Legends, 754 S. Wabash; 427-0333 or 427-1190.