Though half-forgotten and much underappreciated now, Heitor Villa-Lobos (1887-1959) was in his time the most celebrated of Latin American composers, a man of all genres who produced a vast number of works of varied quality but whose piquant originality shone through nonetheless. Undeservedly dismissed in some quarters as salon music--possibly because of the composer's association with Milhaud and the likes in his Parisian days--the quintessential Villa-Lobos mixes Afro-Brazilian color and rhythms with continental urbanity; its appeal is not unlike Stravinsky's in seeming exotic and familiar, naive and sophisticated all at once. To mark (belatedly) the centennial of his birth, the Chicago Ensemble has scheduled the Suite for Soprano and Violin, a minor masterpiece from the early 20s noted for its wild exuberance and inventiveness. Also included on the CE's typically bountiful program are: Lukas Foss's Three Pieces for Flute and Piano (1943), an early exercise in defining American neoclassicism originally scored for the violin but recently transcribed for flute by the composer, and Faure's Piano Quartet no. 1, a gem of French romanticism cultishly cherished by those with a taste for exaggerated languor and melodic flights of fancy. Among the soloists are flutist Susan Levitan and soprano Doris Kirschner. Note: the CE, which long ago established a reputation for excellence and endearing rapport, is undergoing an identity crisis due to recent changes in its roster; the resulting unpredictability has curiously blunted its penchant for occasional didactic dullness. Saturday, 8 PM, Rosary College, 7900 W. Division, River Forest. Sunday, 2:30 PM, Unitarian Church of Evanston, 1330 Ridge, Evanston. Tuesday, 8 PM, Mandel Hall, University of Chicago, 5706 S. University. 292-1060.