Legendary pianists don't fade away; they count on disciples and spouses to keep the flame going. Such is the case with Mieczyslaw Horszowski. In a distinguished career that started at the turn of the century, when he was nine years old, and ended a year ago with his death, the Polish-born pianist was best known as a first-rate accompanist and teacher. His playing style, which can be traced to Beethoven and Czerny, had an old-world aura, graceful and melodic yet forceful and precise. It's only his reticent personality, one suspects, that prevented him from reaching the stardom of his contemporaries Horowitz and Rubinstein. Within the musical circles he was greatly appreciated; among his students at the Curtis Institute were Peter Serkin, Murray Perahia, Richard Goode, and other bright lights of our time. Now Bice Horszowski, his 60ish Italian-born widow and longtime assistant, is continuing the legacy. An accomplished keyboardist who studied with Alfred Cortot and her husband, the shy Mrs. Horszowski seldom performs in public. At this memorial recital, she'll play pieces by 19th-century composers for whom Mieczyslaw felt a particular affinity. Included are Schumann's Arabeske, three rippling romantic riffs by Alfredo Catalani, and Beethoven's transcendental Sonata no. 31. Tuesday, 12:15 PM, Preston Bradley Hall, Chicago Cultural Center, 78 E. Washington; 346-3262.