Birgit Nilsson (1918-2005), the world-famous opera soprano nicknamed 'la Nilsson', had a long and illustrious career. She was the court singer most associated with Wagner and sang in the greatest opera houses in Europe and the United States.
On lennartnilsson.com you can read about this specific photograph:
"Birgit Nilsson sings Elektra for the first time at the Stockholm Opera in 1965. It was also her last opera role, in Frankfurt in 1982. Nilsson received permission to photograph her in that role in 1966, on behalf of Life Magazine.
In her book 'That was LIFE', from 1977, Dora Jane Hamblin writes: 'When Birgit went back to Sweden for the premiere of a role she intended later to sing at the Metropolitan Opera in Manhattan, a picture assignment editor asked Lennart to cover her Stockholm opening. For a day or so there was silence. Then came a cablegram, Wagnerian in its outrage, from that great Wagnerian, Birgit.

'Lennart Nilsson, no kin,' it said (Birgit had picked up Time Inc. style during her years in New York), not only wants to photograph me at the opera house, he also wants me to swallow that little camera to photograph my vocal cords. This I will not do because I know where it has been.' Signed Birgit Nilsson.'

Nilsson did not succeed in photographing her vocal cords that year (1966), but in connection with the film "Lennart Nilsson - The Master Photographer" (1996), the world star accepted. 30 years later."