Most classical crossover music demeans both the popular and classical genres. Contempo--formerly the Contemporary Chamber Players--is trying to do crossover right, including smart music and musicians from both genres on the same bill. On this one, jazz pianist Brad Mehldau will improvise solo, and judging from his recent live album, he'll be aiming for something along the lines of Keith Jarrett's loose-limbed improvised concerts. The program also includes works in the avant-garde tradition CCP has long been known for. Eighth Blackbird, soprano Valdine Anderson, and conductor Cliff Colnot will perform the 1985 song cycle Song Offerings by Jonathan Harvey, a standout British composer whose works display a discreet use of color and unobtrusive accompaniment. In this setting of four Tagore poems for string quintet, flute, clarinet, and piano, the soprano vocalist is on a journey toward her lover--or is it master? The poetry is intentionally vague. The program opens with the Pacifica Quartet performing George Crumb's brilliant Black Angels for amplified string quartet. Written as a response to Vietnam, it depicts the psychological wounds of warfare, even in its starkly placid moments. Crumb said recently that the feelings that led him to write it are mirrored in his feelings about America's current wars. Chen Yi's Qi, for flute, piano, cello, and percussion, will also be performed. Tuesday 26, 7:30 PM, Rubloff Auditorium, Chicago Historical Society, 1601 N. Clark, 773-702-8068, $35 in advance, $40 at the door.