[1] In 1931 he was engaged by Arturo Toscanini to sing in Bayreuth and appeared there as Ritter in Parsifal, Reinmar in Tannhäuser and Steuermann in Tristan und Isolde.
In 1938 he went on tour in the United States with the Salzburg Opera Guild and stayed there for two years before returning to Hungary.
[3] After World War II ended, Ernster appeared in Basel and at New York's Metropolitan Opera where he made his debut on 20 November 1946 as King Marke in Tristan und Isolde.
His last opera performance was in Budapest in 1966 when he sang Sarastro in Die Zauberflöte at the Margaret Island open-air theatre.
[6] His sister, Adelina Ernster (died 1963, New York), was also an opera singer and performed primarily in Frankfurt and Hamburg.