Bright Sheng's H'un (Lacerations): In Memoriam 1966-76 and Robert Beaser's Double Chorus are, respectively, the seventh and eighth works to be premiered by the Chicago Symphony in its still-young season--a count unprecedented in the CSO's play-it-safe Solti era. Sheng, a Shanghai native who emigrated to this country in 1982 and is currently the Lyric Opera's resident composer, has encapsulated in his 20-minute orchestral tour de force the turmoil and anguish of the Cultural Revolution, of which he was a victim. According to him, the fast and furious first half depicts the social unrest and the bottom half contemplates, in pain and regret, the aftermath. The piece makes no concession to melody but relies on rhythm and instrumental color to sustain its emotional ferocity; it was first runner-up for the 1989 Pulitzer Prize. Double Chorus, one of the symphony's centennial commissions, could be aptly described as a study in formalism. An example of the New York-based composer's interest in musical dialogues between pairs of, opposites, this ten-minute work explores the euphonies created by interweaving the sounds of various instrumental dusters (or choruses, hence the title). Both Sheng and Beaser are in their mid-30s and embarking on noteworthy careers. The remainder of the program consists of a pair of French golden oldies: Saint-Saens' Violin Concerto no. 3 and Ravel's Mother Goose. The violin soloist is David Taylor, the CSO's assistant concertmaster; the conductor is Kenneth Jean. Tonight and Saturday, 8 PM, and Tuesday, 7:30 PM, Orchestra Hall, 220 S. Michigan; 435-6666 or 435-8122.