The vibraphone is an instrument that’s become peculiar to jazz–how often do you hear it in any other kind of music?–and Bobby Hutcherson is unique among vibists. The three other major practitioners, Lionel Hampton, Red Norvo, and Milt Jackson, are all straight-ahead players; Hutcherson dwells wholly in realms of fancy. Temperamentally he’s a romantic, given to long solos that are streams of melody, flowing smoothly, meandering in odd directions, or crashing through wild harmonic rapids. It’s his high harmonic sophistication that allows Hutcherson to rove so freely–he’s a modal, post-hard bop improviser who can venture very near free playing even in standard material. His solos offer all kinds of quirky delights, including misterioso atmospheres, whimsical mockery, and obsessive variations on small melodic or rhythmic figures. But however capricious his music, it’s always done with a fine, urgent swing. He’ll be abetted by the stimulating pianist Willie Pickens, bassist Larry Gray, and drummer Wilbur Campbell. Tonight and Saturday, 9 and 11 PM, Joe Segal’s Jazz Showcase, Blackstone Hotel, 636 S. Michigan; 427-4300.