Pushing 30, this venerable new-music extravaganza - part of the River to River festival - will last eight hours this year. Among the impressive lineup of performers are vocal artists like Anonymous 4, singing selections from "love fail," by David Lang, a Bang on the Can founder); Roomful of Teeth; and Meredith Monk. The instrumentalists include So Percussion; the ensemble Contemporaneous, playing Andrew Norman's "Try"; and the resident Bang on a Can All-Stars. The mood is always delightfully loose and the music a rich swath, heavy on American composers.