The nature of American society is such that Howard Johnson will always be best known as "that guy who plays the big saxophone on Saturday Night Live"--despite the fact that his virtuosity on the baritone sax has been employed by Taj Mahal and Paul Butterfield, Gil Evans and Dizzy Gillespie, Jack DeJohnette and Abdullah Ibrahim and three dozen other leaders who decide they want the top gun for the bottom sounds. But Johnson's impact extends beyond (and even beneath) the bari sax; as the most widely admired practitioner of the jazz tuba, he has revitalized that musical behemoth, making the instrument that's been around since the earliest jazz bands marched through the streets of New Orleans into a viable, even desirable, solo instrument in modern jazz. Johnson plays the tuba as dexterously as the trumpet, which is also in his repertoire; more important than the mere spectacle, though, is his sheer musicianship, which extends beyond his choice of tools. Johnson's Chicago performance finds him in the company of vocalists Joan Bouise and Rita Warford; bassist Harrison Bankhead and drummer Dushun Mosley round out the local contingent. (And just for the record, Johnson not only played in the Saturday Night Live band; he's also credited with organizing the band for the show's debut, and he took over as leader in the fifth season. The show started heading downhill right about the time he left, but that was probably a coincidence.) Next Saturday, December 29, 8 PM, Southend Musicworks, 1313 S. Wabash; 939-2848.