He was recruited by soprano Rosa Ponselle as an accompanist and assistant conductor for the Baltimore Opera Company (then the Baltimore Civic Opera). He remained on the opera company's staff as music director and for many years translated opera libretti, which were projected as surtitles at the Lyric Opera House. He was named music director emeritus in 2002.

Yannuzzi judged numerous vocal competitions and accompanied and mentored aspiring singers. Metropolitan Opera bass-baritone James Morris, who met Yannuzzi when he auditioned for Ponselle in 1965, told the Sun, "He taught me my entire repertoire and possessed an incredible musical knowledge, He was a complete original, a one-of-a-kind musician. There is a void in the opera world today."

Michael Harrison, the company's director, told the paper, "He was an extraordinary musician and teacher who was absolutely devoted to the opera company. When you sat down with him with an opera score, you learned so many new things. He was invaluable. He had so much musical knowledge."

Yannuzzi died of pneumonia complications at Maryland General Hospital.