Aside from Blair’s sickening make-up, the other key terrifying part of the character is its demon voice.
Compare the before and after above, as Blair’s voice is replaced by something growling, reedy, and sinister.
The final demon voice was created without any significant post-production alteration by an Academy Award-winning actress who went to dangerous lengths to create it.
“I had a lot of trouble devising how the demon would sound,” Friedkin said. “If you read the novel, it says ‘The voice was terrible’ or ‘It was frightening’ … But how do you achieve that?”
He came up with the notion that the voice should be gender neutral, neither male nor female.
“I remembered from dramatic radio, this great actress Mercedes McCambridge, who worked a lot with Orson Welles and the great radio performers. I remembered she had a kind of neutral sound,” the director recalled. He tracked her down to a stage production of Who’s Afraid of Virginia Woolf in Dallas, and got her to come see a rough cut of the film.
“Afterward, she said: ‘Do you know anything about me? What do you know about me?’” he recalled. “I said, ‘Only that you’re a really great actress and I remember your voice from 25, 30 years ago.’
“She said, ‘Well … I’m a practicing Catholic,’ she said, ‘And I am also a drunk. I went through AA, and I’ve had many deep psychological problems, and the church has been like a rock for me.’”
It seemed like she was getting ready to turn down the project, but instead told him: “’I know what you want me to do for this voice.’”
Then she added: “’If I do that … I’m going to start drinking again.’”