J.J. Johnson's return to public performance has something of a mythic quality. Johnson, who was the first to adapt the bebop innovations of Parker and Gillespie to the trombone, had long held a legendary position in modern jazz anyway; and because he was there almost at the beginning, his name--not to mention his cool, dry sound and slipstream technique--seemed carved into jazz history. But in the late 60s Johnson disappeared from jazz, moving to Los Angeles to become a successful composer for film and TV. So his return to performing some 20 years later had an extra kick: to a generation of listeners who had heard his records but never seen him, it was almost as if he'd risen from the dead. At his last Chicago performance, Johnson gave glimpses of the phenomenal control of the slide trombone that in one swoop lifted the instrument into the front ranks of modern jazz and birthed virtually every trombone style of the last 40 years. It may be unreasonable to expect him to convey a new message after his long absence, but the old one still comes across with clarity and some force. I imagine that this engagement, which includes the take-no-prisoners tenor saxist Ed Petersen, will galvanize all of Johnson's resources. Tonight through Sunday, Joe Segal's Jazz Showcase, Blackstone Hotel, 636 S. Michigan; 427-4300.