After appearing in several operetta productions in minor theatres and singing in cabaret performances in New York City for a few years, Harrold finally had a big break in his career when he drew the attention of Oscar Hammerstein I in 1909. Hammerstein "discovered" the singer while attending an operetta he was in at the Victoria Theater. Hammerstein took the singer in hand and put him under the tutelage of voice teacher Oscar Saenger; paying for the singing lessons himself. Harrold later pursued further studies in Paris in 1912–13.