Certain jazz musicians display an essential command of their instruments that verges on symbiosis: above and beyond the concerns of their art, their grasp of their instruments' natures leads to the exclamation "Oh, that's how it should be played!" Solo pianist Dave McKenna fits this category. Melodically and formally, McKenna's strengths lie in the elevation of familiar skills: his arrangements call for the same two-part inventions or full-chorded choruses used by most solo pianists. But his unerring use of these elements, along with an irrepressible rhythmic vitality, subtly separates him from the pack. Subtlety is rarely the concern of McKenna's always active left arm, which seems as powerful as that of Frank Viola (the current southpaw ace of McKenna's beloved Boston Red Sox). Few bands could ask for a rhythm section as propulsive or imaginative as McKenna's left hand: his walking (at times galloping) low-register lines could serve as models for aspiring bassists, and when that some hand sets and maintains a hefty stride pattern, it becomes perhaps one-third of a decent drum set as well. On up-tempo tunes, the music barrels along as if it had a locomotive at its back. Monday, 7:30 PM, LaSalle Ballroom, Holiday Inn Chicago City Centre, 300 E. Ohio; 787-6100 or 708-675-6331.