At the 1933 Bayreuth Festival, the year of the Machtergreifung by the Nazis, the singer took over the role of Magdalene in Wagner's Die Meistersinger von Nürnberg, directed and conducted by Heinz Tietjen.
There she sang a wide range of mezzo and contralto parts from the classical repertoire, including four central Verdi roles, Azucena, Eboli, Amneris and Emilia.
In the German UFA feature film Fürst Woronzeff by Arthur Robison from 1934, Berglund - together with the tenor Walther Ludwig - appeared in the duet of Samson and Dalila from the opera of the same name by Camille Saint-Saëns.
In the 1937 Bayreuth premiere cast of Parsifal new production by Tietjen, but this time with Wilhelm Furtwängler at the podium, she sang the "voice from above" and embodied one of Klingsor's magical girls.
At her home base, the Deutsche Staatsoper Berlin, she increasingly embodied German repertoire: in 1936 she sang in the cheerful opera Schirin und Gertraude by Paul Graener, which is today as forgotten as the two world premieres - Rembrandt and Schloß Dürande - in which she took part.
Auber: Bizet: Debussy: Mozart: Mussorgski: Puccini: Saint-Saëns': Richard Strauss: Tschaikowski: Verdi: Wagner: A recording with the voice of the singer, the Frauenterzett with Tamino from Mozart's The Magic Flute, with Helge Rosvaenge, Hilde Scheppan and Elfriede Marherr, published in the series Große Sänger Große Oper by Top Classic Historia on vinyl in 1971, performed by the Berliner Philharmoniker conducted by Sir Thomas Beecham.