Yes, the very same. The man who created the Tonight show over 40 years ago, that tall bespectacled hipster who went on to host no less than four variety shows for network TV--that Steve Allen--indulges his musical side at the Jazz Showcase. Allen has managed to maintain his jazz credentials throughout his career. He tickled the piano on the very first telecasts of Tonight; and somewhere between "Man on the Street" interviews and "Mad Libs" and the "Camera on the Street" bits that inspired David Letterman's guerrilla television, he managed to write literally hundreds of songs--including the pop standard "This Could Be the Start of Something." For all his wiggy, bop-era humor, Allen plays an unreconstructed style of swing piano, replete with busy filigrees, cafe society chords, and straightforward rhythms. From the recorded evidence--most recently the 1993 Concord album Steve Allen Plays Jazz Tonight--he plays that style pretty well, although the question of whether he could carry an entire jazz performance would certainly stir some debate. Luckily he doesn't have to. His Chicago sojourn features several of the city's most versatile veterans--drummer Charles Braugham, bassist John Whitfield, trumpeter Art Hoyle, and Larry Novak, who will play a second piano--presumably freeing Allen to extemporize verbally as well as musically. Will they constitute another "meeting of the minds" (to recall the name of Allen's PBS talk show, which assembled actors playing historical figures from different eras)? Tune in and find out. Friday through Sunday, Joe Segal's Jazz Showcase, Blackstone Hotel, 636 S. Michigan; 427-4846.