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The soprano Birgit Nilsson was famed for her powerful and expressive voice, which was able to project over large concert halls and opera houses. She was particularly known for her portrayals of Wagnerian heroines, such as Brünnhilde in Die Walküre and Isolde in Tristan und Isolde. Nilsson's voice was also known for its clarity and purity, which allowed her to sing long, sustained notes with ease.