Composer and teacher, he studied composition with Paul Fetler at the University of Minnesota, orchestration privately 1956-8 with Antal Dorati, and composition in 1956 with Goffredo Petrassi at Tanglewood and on a Fulbright Fellowship 1958-60 with Josef Rufer and Boris Blacher at the Hochschule für Musik in Berlin and Luigi Nono in Darmstadt. He taught at the Hochschule as an assistant to Blacher 1958-60 and at the universities of Minnesota 1962-4 and Texas 1964-8 before joining the Faculty of Music at the University of Toronto in 1968. Klein's compositions, which have won Rockefeller New Music prizes (1965 and 1967), the Greenwood Choral Prize, and the Floyd S. Chalmers Performing Arts Creative Award, reflect influences as disparate as Varèse and jazz.