In 1976 Keene conducted the world premiere of Gian Carlo Menotti's The Hero for the Opera Company of Philadelphia. He also conducted at the Metropolitan Opera during a single season, a double-bill of Cavalleria rusticana and Pagliacci (with Teresa Stratas as Nedda) in 1971. From 1974 to 1989, he was Music Director of the Artpark Festival in Buffalo, and from 1975 to 1984 held the same post at the Syracuse Symphony Orchestra. He was Founder of the Long Island Philharmonic in 1979, and directed it until 1990. In 1976, he led the world premiere of Carlisle Floyd's Bilby's Doll at the Houston Grand Opera.
