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In page Erna Berger:

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Berger made her debut at the Metropolitan Opera in 1949.[6] In October 1949, May and June 1951, she sang three Gildas (Rigoletto) at Covent Garden, London. During the 1949/50 and 1950/51 seasons, she appeared in Der Rosenkavalier (opposite Eleanor Steber and Risë Stevens, conducted by Fritz Reiner and directed by Herbert Graf), Rigoletto (with Warren, then Enzo Mascherini), Die Zauberflöte, and Il barbiere di Siviglia (with Giuseppe Valdengo). She also sang Woglinde and the Waldvogel in Der Ring des Nibelungen, with Kirsten Flagstad and Helen Traubel alternating as Brünnhilde.[citation needed]