When supervising sound editor Alan Robert Murray sat down to talk with director Todd Phillips about their sonic approach to Warner Bros.' Joker, the filmmaker said he wanted realistic sounds instead of the typical tones expected in a comic book-inspired film.

"He didn't want overdone punches and sound design that made it seem unrealistic," says Murray, a two-time Oscar winner (American Sniper, Letters From Iwo Jima) who earned his 10th career nomination — a record for sound editing — with Joker. "So it was more of following Arthur's descent into madness. Everything would start off normal, and then our sound effects reacted to what was going on with Arthur."

For a sequence in which Arthur Fleck (Joaquin Phoenix) is beaten up by three Wall Street suits on a subway car, Murray explains that the sound gets more sinister as the scene progresses. "It was building the scene, starting at a normal atmosphere and then amping it up as the torment increased on Arthur," he says, adding that this included sounds such as the screech of the subway car. "On top of that, the trains going by in opposite directions took on a sinister sound. They were made up of processed jets and roller coasters and anything that was dark and gritty to bring the whole thing with Arthur into perspective."

Another example of how the film used sound to reflect Arthur's state of mind is in the opening scene, which shows Arthur working as a clown when gang members steals his sign; he chases them into an alley and is attacked. For the gritty and early '80s feel, Murray used period sounds such as vehicle noises with V8 engines and mufflers from muscle cars. "As we got deeper into the scene, the sounds of the city got harsher and louder. It was accented by sirens to keep that gritty, nasty, always threatening feel of Gotham," he says. "We had to create sirens that were not New York, but something committed to Gotham, so we ended up crossing from regular sirens into a more European flair."

Murray adds that to make the audience "feel that they're right there with Arthur," they recorded sounds with an ambisonic (surround sound) mic, "which helped in the Atmos mix."

And with Arthur's final transformation into Joker in front of a rioting crowd on the city's streets, Murray notes that "nobody's ever chanting things like 'Joker, Joker.' It's more of a wounded animal cry out from the crowd. He's now become total Joker."

The work on this sequence involved gathering a group on the New York set of the Warner Bros. lot. "We recorded specific yell outs, but not words. More like a warrior's scream," says Murray, who also incorporated processed animals sounds, including lions and wolves, into these crowd vocalizations.

Hildur Gudnadóttir's haunting score also was a key factor in creating the sound. "Our director would decide what was going to start the scene — either Hildur's score or we would come in with a tonal sound. And we would trade off during the scene."

This story first appeared in a January stand-alone issue of The Hollywood Reporter magazine. Click here to subscribe.