Zelma Watson George, 90, activist and the first African American woman to play a leading role in an American opera on Broadway. Mrs. George was chosen by composer Gian Carlo Menotti to sing a revival of his opera "The Medium" in 1950. She also sang several operatic roles in Cleveland, where she lived most of her life. But she was better known as an activist and social reformer. After 10 years as dean of women at Tennessee State University in Nashville, Mrs. George moved to Cleveland in 1942 on a Rockefeller Foundation grant to study the music of blacks. From 1966 until she retired in 1974, she was executive director of the Cleveland Job Corps Center for Women. In 1960, President Dwight D. Eisenhower named her an alternate on the U.S. delegation to the United Nations. On July 3 in Cleveland.