 On January 11, 1948 he gave his New York City recital debut at Town Hall.Shortly after his Town Hall recital, Cassel was approached by Laszlo Halasz to join the roster of principal singers at the New York City Opera (NYCO).Cassel jumped at the chance and made his debut with the company on April 1, 1948 as Scarpia in Giacomo Puccini's "Tosca" opposite Wilma Spence in the title role and Rudolph Petrak as Cavaradossi.