Greg Osby's fierce commitment to evolution is particularly notable now, deep in the second decade of his career--a time when many jazz players settle into routine. The saxophonist's bands are always changing (although that's partly because some of his former sidemen, like pianist Jason Moran, have developed strong solo careers of their own) and so are the concepts he brings to recording: St. Louis Shoes was a systematic reassessment of the music he grew up with; on Symbols of Light (A Solution) he used a string quartet to create habitats for improvisation. The latest, Channel Three (Blue Note), is his first trio album in 18 years as a leader. In the liner notes he admires the great saxophone trio recordings of jazz history and explains that he didn't want to add anything merely lukewarm to the tradition, and he certainly hasn't: supported by young bassist Matt Brewer and explosive veteran drummer Jeff "Tain" Watts (a regular in the Branford Marsalis band), he's made some of his most searching, edgy music to date. In the absence of a conventional harmony instrument like piano or guitar, his daring solos are rangier and more jagged than ever but remain disciplined as always. Osby's originals, bookended by terrific personalized readings of Ornette Coleman's "Mob Job" and Eric Dolphy's "Miss Ann," are mostly improvisational vehicles, each exploring a specific gambit: slack 5/4 funk ("Viewer Discretion"), tricky sax-bass unison lines ("Vertical Hold"), or a tightly constrained melodic range ("Test Pattern"). There are also pin-drop duets with Brewer and extroverted duck-and-weave showdowns with Watts; at every turn the trio refuses to take the easy route. Osby unveils yet another new lineup on this visit--joining him and Brewer are pianist James Gordon Williams and drummer Tommy Crane. Fri 9/9/, 9 PM, Green Mill, 4802 N. Broadway, 773-878-5552, $12. See also Saturday.