[4] In 1958, she appeared at the Bayreuth Festival for the first time, making her stage debut, as Floßhilde and the Second Norn in Der Ring des Nibelungen conducted by Hans Knappertsbusch.

[1][8] She appeared at the Vienna State Opera, first in 1960 as the First Norn in Götterdämmerung,[9] and in 1963 at La Scala in Milan as Iocaste in Stravinsky's Oedipus Rex.

With the Hamburg ensemble, she appeared in Florence, the Metropolitan Opera in New York City, the Opéra de Montréal, the Mariinsky Theatre in Saint Petersburg, in Moscow and in Tokyo.

[4] Boese took part in world premieres, such as Mrs. Bradshaw in Alexander Goehr's Arden muß sterben in Hamburg on 5 March 1967,[8] and as the Schwarze Nachbarin in Udo Zimmermann's Die wundersame Schustersfrau at the Schwetzingen Festival on 25 April 1982.

[4] In 1973, she appeared as Ulrica in a new production of Verdi's Un ballo in maschera, alongside Luciano Pavarotti and Sherrill Milnes.