Carmela was already an established singer in vaudeville after her debut in The Girl from Brighton, a 1912 Broadway musical. Three years later, in 1915, Carmela brought Rosa to audition for her vaudeville agent. In spite of being markedly overweight (a stark contrast to the fashion-model physique of her older sister), Rosa impressed with her voice, and she was hired to perform with Carmela as a “sister act.” Between 1915 and 1918, the Ponzillo Sisters (also known as “Those Tailored Italian Girls”) became a headlining act on the Keith Vaudeville Circuit, appearing in all the major Keith theaters and earning a substantial income in the process. The sisters’ act consisted of traditional ballads, popular Italian songs, and operatic arias and duets.
In 1918, Carmela and Rosa demanded a substantial fee increase from the Keith Vaudeville Circuit, as a result of which their act was dropped. At the time, Carmela was studying in New York with a well-connected voice teacher/agent named William Thorner. Thorner auditioned Rosa, and agreed to give her lessons. (Rosa later denied that Thorner had ever given her voice lessons, but her statements on the subject are contradictory.) Although initially less impressed with Rosa’s future prospects than with Carmela’s, Thorner changed his opinion after the legendary baritone Victor Maurel, whom Giuseppe Verdi had chosen to create Iago in Otello, auditioned both sisters at his friend Thorner’s request. Soon afterward, Thorner persuaded the great tenor Enrico Caruso, star of the Metropolitan Opera, to his studio to hear Carmela and Rosa sing. Caruso was deeply impressed with Rosa’s voice and arranged for an audition with the Met, as a result of which the Met’s general manager, Giulio Gatti-Casazza, offered Rosa a contract for the 1918-19 season.