 In 1961 he made his debut with the Philadelphia Lyric Opera Company as Friedrich von Telramund in Wagner's "Lohengrin".From 1970 to 1972 Cassel sang the role of Johann Strauss Sr in Korngold's "The Great Waltz" in London, and then performed in Italy and Spain for a couple years.After retiring from the stage, Cassel began a long teaching career at Indiana University in 1974.