Radcliffe and his deathly hallows Courtesy A24

Ever since its Sundance premiere, Daniel Scheinert and Daniel Kwan’s Swiss Army Man has been known as the movie in which a shipwrecked Paul Dano rides Daniel Radcliffe’s farting corpse to civilization. It’s actually about a lot more than that, but it almost certainly contains the most diverse, complex array of farts ever heard onscreen. So where did all those farts come from? We asked the film’s sound mixer, Steve Nelson, and supervising sound editor, Brent Kiser, to let us in on their secrets.

What is the biggest challenge about recording a fart?

Nelson: The biggest part is timing. Secondly, if you’re coming to me to have your fart recorded, you want to make sure that you have an audible one and not a silent one. But it can be hard to predict in advance what kind of fart it will be.

How did you go about recording farts for this film?

Nelson: In my case, I came to work on set one day, and the directors made an announcement: “If anyone has a fart that they would like to donate to the movie, see Steve at any point during the day and fart for him.” We did have a fairly good participation, but maybe not as many as they had hoped for. I think people get really camera-shy. We’re socially ingrained to save up our farts until after work; you have to adjust your mindset to start intentionally farting outward.

Were there any particularly memorable farts you recorded?

Nelson: The first person to do it immediately after the directors’ announcement was our cable person on the sound department. She volunteered and gave a really good one. And the second one I remember was Paul Dano, who cut one loose right before a take. He just grabbed the boom mic right out of the air and delivered it. We made note so that the editors could easily find that one.

Kiser: I definitely remember that one! Steve’s recordings are some of the best I ever got from a production mixer; he went above and beyond and gave us all sorts of stuff that we didn’t expect. But we only wound up using one real fart in the movie. It’s toward the end when they’re talking about thoughts, when they’re up in the tree: “This is a thought…this is a thought…” The second or third Paul Dano fart in that montage is Matt Hannam, the picture editor, farting. He was so good to us, and he was like, “Please, please put in one of my farts.”

How were the other farts recorded?

Kiser: Right after the shoot, the directors came in and we had a six- to eight-hour fart-recording session. We just thought of every way we could to make these farts: We needed underwater farts, we needed airy farts, we needed farts that were not cartoonish, that were realistic but at the same time expressive. I know — my career. Mom’s really happy I went to art school. So we got a little fart library together that we then gave to the picture editor team. And in the opening scenes, when Paul Dano is listening to Daniel Radcliffe’s body for his vitals, to see if he’s alive, we had a slow rumbling internal gestational sound: That’s actually Daniel Scheinert’s stomach growling.

What are some of the best artificial ways to create fart sounds?

Kiser: First we got real elementary-school with it, like putting our hands up to our face and [blowing]. But we found that only worked with Dan Kwan, because he didn’t have facial hair, and it won’t work if you have facial hair. Of course, we never knew that in third grade. Same thing with the arms: Once again, works better on people that didn’t have defined muscles. And chubby cheeks make really good fart sounds.

We also did things like blow through a pipe into a mixture of liquids to try to get bubbles. One challenge was creating the “butt jet,” or the fart Jet Ski. We needed to have the rev, and the motor, to give the feeling that it was mechanical. We really layered up a lot of sound on that one — water bubbles, airy farts, some slowed-down Jet Skis, some other motor engines — to give the feeling and presence of…butt-jet.

It must have been quite a challenge to create these farts in such a way that they can be distinctive, and audible, but still feel like a part of the film. They’re funny, but not in a Mel Brooks way.

Kiser: The whole thing started with one simple log line: The directors wanted to create a movie that would open up with a fart that you would laugh at and end with a fart that you would cry at.

And real farts, especially if you’re outside, aren’t really that audible. So, for example, in the opening scene, when Paul Dano is off trying to hang himself, and he sees Daniel Radcliffe’s corpse way off down by the beach, farting up a storm — in real life, he wouldn’t be hearing that.

Kiser: We ended up using a lot of focused sound. In real life, we can cancel out other things around us. So how do we seamlessly get into this situation and drown out the ambient noise, and make the sound more focused, pointed? We built out the ocean really big at the beginning, and then we brought it down slowly, so that we’re able to help you focus on what the directors want you to focus on: We can direct your attention to these farts and the tension that they’re creating while Paul Dano is trying to hang himself. “Dude, I’m just trying to die. Can you quit this shit?”

The sonic landscape in general for this film is interesting. It’s a castaway movie, and we know how important sound is in films like that — Crusoe, Cast Away, etc. But it’s also very surreal, and they’re not actually on a desert island, it turns out, so the world we’re hearing is probably broader than the typical desert island movie.

Nelson: The circumstances of making this film were rather unique. We spent a lot of time hiking around the forest carrying around our corpse dummies. One nice thing when you’re making a small movie is that you can cast your net really wide to capture as many atmospheric elements as possible. Iris, the nice girl I told you about who contributed those farts, one of her other jobs was putting on waders, going out into the streams we were shooting around, and putting foam underneath any babbling part of the river, so we could silence it. That allowed us to record without any interference whatever other natural ambience is happening in that place. Otherwise the sound of a river can be pretty overwhelming, if what you’re trying to get across is a real sincere, quiet moment between a sad guy and a dead guy with a boner.

Is there a Wilhelm Scream of farts?

Kiser: Not as of yet! It’s funny — we actually had a real Wilhelm Scream in this, but we ended up taking it out. Beau Borders, who mixed the film in post with me, is a Skywalker dude; he was nominated for an Oscar for Lone Survivor. He grew up on the Skywalker Ranch, and he knew [legendary sound designers] Ben Burtt and Randy Thom, those heavy hitters of sound — the reason I’m able to do what I do is because of those dudes. I put a Wilhelm Scream in, and he said, “Yeah, I’m not playing that. That’s Ben Burtt’s sound. Only Ben can put that in.” That gave a whole new meaning to the Wilhelm Scream for me. That’s Ben’s signature; it’d be weird if I signed my name with someone else’s.