Composer and alto saxophonist/clarinetist Guillermo Gregorio creates music of spatial and temporal luxury. Born in Buenos Aires 54 years ago, Gregorio has lived all over the world (he currently resides in Michigan City, Indiana) and possesses a broad slate of experience. Though he's worked with an Argentinean Fluxus group, performed the work of 20th-century composers, and led his own jazz-leaning combos in Argentina and Germany, his studies with saxophonist Warne Marsh and his membership in Swiss trumpeter Franz Koglmann's Pipetet are the experiences most evident in his bracingly distinctive music. Gregorio's most indelible influence, however, is pianist Lennie Tristano, the brilliant innovator with whom Marsh cut his teeth and who profoundly impacted Koglmann decades later. On Gregorio's recent debut, Approximately (Hat Art), Tristano's influence is oblique, filtered through Gregorio's daring imagination and measured attack. Centering on unadorned melody while adhering to spacious harmonic concerns, the reedist--whose complex but agile alto machinations recall the work of Marsh and fellow Tristano disciple Lee Konitz--is joined by various combinations of additional sax, violin, bass, and piano (drummerless a la early Tristano). Despite the music's airiness and moderate tempos, there's nothing "cool" about it. With a chamberlike feel the musicians develop impressive melodic schemes, expressing both delicate harmonic support and beautiful multilinear lyrical filigree. For his Chicago debut Gregorio will be joined by the talented Boston pianist Pandelis Karayorgis (he's on the CD), who masterfully conveys a weighty presence without pulling down the sonic lightness of the proceedings. Wednesday, 9 PM, Empty Bottle, 1035 N. Western; 276-3600.