Irina Arkhipova, a Soviet—era diva who sang at the Bolshoi theater for decades, has died. She was 85.

The director of the Arkhipova Foundation said the singer died on Thursday at Moscow’s Botkin hospital. A cause of death wasn’t specified.

Arkhipova, a mezzo-soprano and later contralto, sang leading roles for the Bolshoi for decades after joining it in 1956. She reached the peak of her career in the 1960s and 1970s, making guest appearances throughout Europe and the U.S.

Her most celebrated roles included Carmen in Bizet’s Carmen, Amneris in Giuseppe Verdi’s Aida, Marina and Marfa in Mussorgsky’s Boris Godunov and Khovanshchina and Helene in Prokofiev’s War and Peace.

Her full and rich voice has been admired for great power and intensity, and she has been universally praised for technically perfect and highly emotional performance.

President Dmitry Medvedev sent condolences to Arkhipova’s family.