At this essential gig, four composers who hail from the Association for the Advancement of Creative Musicians (or AACM) each present world-premiere chamber works written for the singer Thomas Buckner, a baritone of wry humor best known for his work in the operas of Robert Ashley. In addition to the world premieres from Muhal Richard Abrams, Henry Threadgill, Wadada Leo Smith and Amina Claudine Myers, Buckner also performs some earlier examples of AACM art song (including Roscie Mitchell’s trio of E.E. Cummings settings, and a piece for strings, flute and baritone by the late violinist Leroy Jenkins). While the reputations of these composers seem ever more secure inside the halls of jazz, chances to hear their notated chamber pieces aren’t common. That’s too bad, since these unpredictable, often slashing works shed a unique light on the conceptual efforts of a major, tirelessly prolific new-music movement.