Jimmy McGriff and Hank Crawford swing soulfully along that sweet fault line that runs between down-home blues and uptown jazz. At the heart of their sound though is the uplifting ecstasy of the spiritual tradition that helped give rise to both: Crawford’s alto wails like a gospel singer over the vibrating vocals of McGriff’s famous Hammond B-3 organ, then drops into lower-register purrs and moans that make it sound as if he’s been overcome by an intimate relationship with a very funky spirit. Crawford’s jubilant testifying is so infectious that you may forget to listen to what McGriff is laying down: his melodic imagination and improvisational vision are less flamboyant than Crawford’s, but he’s a master at using tone, dynamics, and subtle chordal variations to complement his partner’s churchy testimonials. McGriff and Crawford usually get categorized as jazz musicians, but McGriff, at least, claims he’d rather be considered a bluesman, and when Crawford’s lines start to writhe and twine around the gritty-sweet imprecations of his keyboards, the better part of a decade of musical tradition comes together in joyful celebration. Saturday, 10 PM, Buddy Guy’s Legends, 754 S. Wabash; 427-0333 or 427-1190. DAVID WHITEIS