Because of Strickland's enthusiasm for creating layered sound designs for both "Berberian Sound Studio" and the nonexistent "Equestrian Vortex," supervising sound editor Joakim Sundström said, "As a sound nerd, it was a once-in-a-lifetime project — this is the one you'd want to do."

Even the scenes depicting Foley work had to be Foleyed like any other scene. "Obviously we had to Foley 'Berberian' more realistically than 'Equestrian,' which we approached in a more '60s-'70s Italian way with close mikes," Sundström added. He had the "Equestrian Vortex" sounds transferred onto magnetic tape and re-recorded acoustically on old reel-to-reel machines in the director Roy Andersson's studio in Sweden "to give a sense of returning the material to its analog origins. It was such an aesthetically pleasing era for sound."

Despite the absence of but a single visible violent act — the cruel high-frequency manipulation of a voice actress to make her scream for real — "Berberian Sound Studio's" sound is all diegetic: Its source is present in the story, if not always seen.

It is Gilderoy, coerced by his producer, who turns up the frequency on the actress in the sound booth, ravaging her ears.

"It's an extension of the Foley — violence by proxy — and it comes at the point when Gilderoy realizes it's all gone too far," Strickland said. "Usually when a character in a film suffers, the audience has no direct relationship to that. My initial idea was to make the audience feel what the character's feeling: You are paying to watch someone suffer, now you know what it's like.

"When we did the mix we used pretty high frequencies, but then I realized I didn't want to be responsible for giving people hearing problems," he added. "You can get away with it in a concert by My Bloody Valentine, but not in a cinema. The only one who suffered was me — I had really bad hearing problems for a few days after that scene."