Complex sentence: New York audience had their first chance to hear the soprano's fine voice in 1960, when she sang there in "Der Rosenkavalier": her performance prompted Lotte Lehmann to call her' the best Sophie in the world'.
Split into simpler sentences: New York audience had their first chance to hear the soprano's fine voice in 1960, when she sang there in "Der Rosenkavalier". Her performance prompted Lotte Lehmann to call her' the best Sophie in the world'.