In 1956, Kastle composed a thirteen-minute "made-to-measure" opera, titled The Swing, for two Singers, a speaking part, and piano accompaniment. It was commissioned by and broadcast on the NBC television network on Sunday, June 10, 1956, at noon. He also wrote The Pariahs, about the sinking of the whaler Essex, a trilogy of operas about the Shakers known under the collective title The Passion of Mother Ann: A Sacred Festival Play, a children's opera called Professor Lookalike and the Children, a piano concerto, sonatas for piano and violin, and three unproduced screenplays, Wedding at Cana, Change of Heart, and Shakespeare's Dog.