Samuel Barber, who died ten years ago, was never an innovator, but he excelled in his narrow niche as an expressionist of personal emotion. In the 30s and 40s, he was a golden boy, one of the last romantic holdouts against the tide of serialism; by the mid-60s, his seldom-changing style had become an anachronism. He embraced traditional highbrow taste and shared Gian Carlo Menotti's aversion to dissonance. Those inclinations may have been responsible for the critics' posthumous devaluation of his reputation, but some of his works, when given the chance, can still cast a potent spell. Three lesser-known Barbers will be performed in this Chicago Symphony Orchestra program (to be performed three times this coming week), each representing a different phase in his life and career. From the 30s his Symphony in One Movement, a neat youthful exercise in modernizing the passacaglia; from the 50s, the 20-minute choral piece Prayers for Kierkegaard, whose spare texture evokes anxiety; and from the late 70s The Lovers, a lush, sensual remembrance sung by a baritone and based on Pablo Neruda's poems. Making his Chicago debut is conductor Andrew Schenck, a Barber specialist who's in the process of recording his entire orchestral works. With the Chicago Symphont Chorus; soloists are soprano Sarah Reese and baritone Dale Duesing. Today, 1:30 PM, tomorrow at 8 PM, and Tuesday, 7:30 PM, Orchestra Hall, 220 S. Michigan, 435-6666 or 435-8122.