Known for its deep-dish pizza, ketchup-free hot dogs, and, apparently, contemporary classical chamber music, Chicago has produced two of the best regarded new music ensembles in the country, eighth blackbird and Ensemble Dal Niente. Like their capitalization-averse neighbors, Ensemble Dal Niente doesn’t shy away from head-scratching experiments—they once did a whole set of variations of Deerhoof songs—and so they make a good choice to debut a new work by trombonist, composer, and computer programmer George Lewis (titled, simply, New Work). Part of the Library of Congress’s invaluable project to commission new music by contemporary composers, the Lewis piece could sound like anything—his pieces marry electronic and classical music, and they’re sometimes built around an interactive computer software program he designed called Voyager. Lewis’ music is paired with that of Austrian “spectralist” composer Georg Friedrich Haas, whose compositional style involves analysis of sound spectrums and subdivisions of octaves and other things that go way over my head, and is so avant-garde that audience members in Pasadena, Calif., once had to sign legal waivers before hearing his music performed. Oct. 30 at Library of Congress Jefferson Building. Free.