For its tenth anniversary, the Chicago Ensemble has slated for repeat performance a number of the greatest hits from its past concerts. The selections ought to remind everyone of the remarkable versatility and range, and the rich programming mix, that are the hallmarks of what many regard as one of the area's two finest chamber groups (the other being Chicago Pro Musica). Look at the works on the program: the gaily sensuous Chamber Sonata (1927) by Frenchman Gabriel Pierne, Sonata for Clarinet and Piano (1952) by American Alvin Etler, Schubert variations, Brahms's Trio for Clarinet, Cello, and Piano, and Private Game for Clarinet and Cello, a 1980 opus by Shulamit Ran. Not one overly familiar piece in the bunch. Such variety (and pedagogical aim) is matched by very few. The result is likely to be music making at its most spontaneous and combustible. Tuesday, 8 PM, Mandel Hall, University of Chicago, 5706 S. University. Saturday, March 21, 8 PM, Rosary College, 7900 W. Division, River Forest. Sunday, Much 22, 2:30 PM, Unitarian Church of Evanston, 1330 Ridge, Evanston. 549-7010.