Rosenblatt was born on May 9, 1882 in Bila Tserkva, Ukraine. The scion of a long line of cantors, Rosenblatt's devoutly religious upbringing prevented him from receiving formal musical training at any of the great academies of his day. He began his career as a member of the local synagogue choir. Quickly lauded as a "wounderkind", or child prodigy, Rosenblatt's solo career was launched. He was known for his extraordinary technique, for the sweetness of his timbre, and for his unique ability to transition from normal voice to falsetto with hardly any noticeable break at all. His technique in cantillation was unique. Notes were hit remarkably accurately at high speeds. Fiorituras, similarly, were struck near perfectly, both rhythmically and on pitch. His fame spread so far that Toscanini appealed to him to sing the leading role in Fromental Halévy's La Juive, but Rosenblatt replied that he would only use his vocal gift for the glory of God, in service to his religion. Notably, he turned down a "Golden Hello" from the Chicago opera house because it violated his religious principles.