Pierre Boulez first wrote his cantata Le visage nuptial in 1946 for a chamber ensemble. Then he spent four decades fine-tuning and reorchestrating the score. The result is one of his richest, most aesthetically satisfying and challenging works: its expressionism recalls that of Berg and Schoenberg; its use of instruments owes a debt to Olivier Messiaen; and its incantatory fervor evokes Stravinsky's Les noces. The text is taken from five poems by Rene Char, a surrealist known for his concentrated violence and sensual imagery. Frankly erotic and diverse in style, the five poems follow the course of a love affair, from encounter to waiting to consummation to appeasement to separation; Boulez came up with an array of appropriate vocal textures for each, from simple litany to 16-part heterophony. The Chicago Symphony Orchestra and its Women's Chorus will be performing the 1989 version. Boulez, whose standards are so exacting that he canceled the Civic's scheduled read-through of Rituel a couple of weeks ago because he felt the players weren't quite ready, will conduct. A big plus are the two soloists, Lucy Shelton and Laura Aikin, both sopranos noted for their expertise in 20th-century repertoire. Also on the program is Bartok's The Miraculous Mandarin, which will be recorded as part of Boulez's survey of Bartok's orchestral music. Friday and Saturday, 8 PM, Orchestra Hall, 220 S. Michigan; 435-6666.