 He made his first stage appearances in a handful of Broadway productions during the late 1930s and early 1940s.He began his opera career at the Metropolitan Opera in 1942, and went on to have a long and fruitful association with that house that lasted until his retirement from the stage in 1974.In addition to working with the Met, Cassel was also a regular performer with the New York City Opera between 1948 and 1954 and worked frequently as a freelance artist with important opera companies on the international stage as well as in the United States.