Phyllis Bryn-Julson made her debut in 1966 in Alban Berg's Lulu Suite, with Erich Leinsdorf (an early mentor) and the Boston Symphony Orchestra in Boston, Providence, RI, and Carnegie Hall in New York. She ultimately sang with this orchestra and the New York Philharmonic Orchestra dozens of times.She made her opera debut in the 1976 world premiere of Roger Sessions' Montezuma in the lead role of Malinche. She made her highly successful debut at the proms in London the following year, again in a modern work, this time Henze's The Raft of Medusa. Later at Covent Garden, she performed in both Le Rossignol by Igor Stravinsky, and L'Enfant et les Sortileges, by Ravel. She has performed the role of Vitellia in La Clemenza di Tito several times in Germany as well as at the Mostly Mozart Festival in New York with conductor Raymond Leppard. At Peabody, she performed the role of Ariadne in Ariadne auf Naxos by Strauss.