1960 – He began conducting opera as a student at the University of California, Berkeley.
1966 – He was appointed assistant conductor of the San Francisco Opera by Kurt Herbert Adler.
1967 – He held the same position at the San Diego Opera.
1972-1975 – Positions held by Keene during his career were music director of the American Spoleto Festival and Syracuse Symphony Orchestra.
1979 – The founder and director of the Long Island Philharmonic and music director of Eliot Feld’s American Ballet Company.
1982 – Keene was a frequent conductor at the New York City Opera during the regimes of Julius Rudel and Beverly Sills, and he joined the permanent staff as music director.
1989 – He assumed the post of general director of the New York City Opera.
1995 – Died on October.
1996 – Keene’s library was donated to Indiana University by his widow Sara Keene.