During the 1960s , she had difficulties with her voice from singing such heavy parts for a decade .
During the 1960s , she returned to singing mezzo - soprano repertoire , such as Klytemnestra in Elektra , the Nurse ( Die Frau ohne Schatten ) and Waltraute .
During the 1960s , she had difficulties with her voice from singing such heavy parts for a decade , and returned to singing mezzo - soprano repertoire , such as Klytemnestra in Elektra , the Nurse ( Die Frau ohne Schatten ) and Waltraute .