For decades New York City and vicinity have furnished the country’s best and brightest contemporary-music performers; but more and more, the west coast is putting up fairly stiff competition. The ten-year-old California E.A.R. Unit, in residence at the LA County Museum of Art, is fast acquiring a reputation for its versatility with instruments and the zestful, entertaining way it approaches the cutting edge. In its Chicago debut, sponsored by Northwestern University’s innovative Computer Music Studio, the nine-member group will present a number of local premieres–including “Revenge Before Breakfast” by avant-garde stalwarts Steve Reich and Frederic Rzewski and “Murphy Nights” by pretenders John Zorn and Henry Brant. One high point of the evening may be “Sealed Room/Cheder Atum” the recently finished piece by Amnon Wolman, a computer-music specialist who teaches at Northwestern. This montage of manipulated sounds (some digitally synthesized) was created as the Israeli-born composer’s emotional response to the gulf war–his family was one of those sheltered in sealed rooms during missile attacks. Saturday, 8:30 PM, Pick- Staiger Concert Hall, Northwestern University, 1977 Sheridan Road, Evanston; 708-491-5441.