How Sound Design Made ‘KPop Demon Hunters’ Sound So Good

The k-pop group Huntrix perform on stage between slaying demons in ‘K-Pop Demon Hunters.’

Netflix

Quite a few elements contribute to the global success of KPop Demon Hunters. The film has a great script, wonderful voice-overs, catchy songs and top notch animation. The emotional reaction of viewers also owes a lot to the sound design that so deftly marries the actors’ voices, the music and accompanying sound effects. While working on the film, sound designer, supervising sound editor and re-recording mixer Michael Babcock thought a lot about the word “harmony.” KPop Demon Hunters is, after all, about the k-pop girl group Huntrix who seek to vanquish demons and restore harmony to the world. Before they can harmonize the world, they need to be in harmony.

“It’s about harmony within oneself,” said Babcock. “Rumi is trying to hide the fact that she’s part demon but also coming to terms with the fact that she’s part demon. She’s trying to get into harmony with herself, but she also has to be able to harmonize with her band mates. There’s harmony in the music, so it’s this clever word that we were able to take and run with to the nth degree. It’s a story word, it’s a sound word, it’s the music.”

Babcock previously worked on the Academy Award winning sound teams of The Dark Knight, Inception and Dune 2: Part Two, as well as the nominated sound teams of Interstellar, Transformers, There Will Be Blood, and War of the Worlds. Having worked on so many major films, did he expect KPop Demon Hunters to become the most popular film on Netflix? Yes and no. It was a special project to work on, but great movies don’t necessarily become popular.

“All I can say is that when working on it, I really felt that we were doing something special, and the fact that it’s gotten discovered is an amazing feeling,” said Babcock. “You never really know sometimes, and especially when you’re in the heat of battle, but this one really felt special even from the beginning. At the end of it, I really hoped people would get to see this. You don’t know. It’s an original story and on top of that it’s a bit of a niche thing. The fact that it’s caught on is absolutely fantastic for a lot of different reasons.”

A sound designer is responsible for all the creative sounds that make a film seem real, magically conjuring up sounds for things that don’t exist and recreating real sounds, such as the metallic clang of fighting swords. All those sounds also have to blend in unobtrusively.

“The sound design has to work with the music,” said Babcock. “The music has to work with the dialogue.”

Babcock listened to k-pop before he began working on the film, enjoying it for both the sound and production values. However, participating in this project allowed him to immerse himself in the music of different k-pop artists. He listened to tracks from BTS, Blackpink, EXO and Psy, then incorporated k-pop music production techniques—such as layered vocals, processing, reverb, delays and k-pop beats—into the film’s sound design.

“I immersed myself in the world to actually inform myself,” said Babcock. “To have a jumping off point as a sound designer, to start building a world for the story based on this whole world of k-pop.”

He began working on this film even before the animation was done. There were storyboards. A lot of the dialogue existed and the crew had the beginning demos of the songs to work with. One of his first discussions with fellow crew members was how to express the demon voices. Gwi-ma has a demon voice he uses. Rumi also has one when she’s connecting with her own inner demons and it’s fittingly scary. Wind chimes and similar elements were used to create a sound for the magical barrier known as the honmoon, the global harmony that Huntrix tries to achieve. Tuning forks were used for the clash of the weapons that Huntrix carries.

“Tuning forks are a musical thing,” said Babcock. “As a sound designer, you’re looking for the genesis of a sound, a sound being organic, and a tuning fork is a musical thing. So it fits into my kind of self-imposed guardrails that something has to have some kind of musical genesis.”

The sound of the tuning forks was then digitally manipulated to fit the pitch of the music and timed to match any moves the characters make.

“The challenge is when you have a lot of music going on is that you have to be able to work within the music,” said Babcock. “So, to me, as a sound person, that means a couple of things. That means you have a certain kind of sonic real estate. There’s certain frequencies you want to use so they can be heard over the music and it has to work, particularly pitch-wise with the music.”

Sound design was integral to many of the film’s iconic scenes, such as the initial appearance of the Saja Boys when they sing “Soda Pop,” the battle scene at the bathhouse and the film’s stirring finale. Babcock said he woke up many mornings with the song “Soda Pop” in his head, an experience much of the world would have once the movie came out.

“Luckily, those songs are fantastic, and the fact that it’s actually a hit in the k-pop world is amazing,” said Babcock. “I think the songs are catchy for a reason. They’re really well done. They’re really well produced and they’re really good.”

He describes the “Soda Pop” sequence as having to be both “cute” and “warm.” That was a challenge from a sound standpoint.

“I had some really great conversations with Maggie and Chris, the directors,” said Babcock. “Maggie’s Korean and she knows this whole k-pop world really well. Also, there’s a Korean cultural element to this. There’s a cuteness in general, and it’s actually harder, more of a challenge to come up with something that’s warm and cute than it is to come up with something really aggressive and angry. So, that particular sequence, it’s all about just running with the themes, the shockwaves that go by the honmoon. It has all that wind chime thing, but it’s also sweetened with “Soda Pop” lyrics going by in bubbles.”

Sound effects for the “Soda Pop” scene included manipulated bubble sounds. Babcock is particularly fond of how the bathhouse scene turned out.

“That is a really good example of all the different food groups of sound working together, literally going from event to event, and it has to be driven by music,” he said. “That’s an example of where all the movements you hear are working in rhythm within music, all the tones. You hear all the weapons, all the whooshes and all the crazy fight stuff going on is all working with the music, and you’re also making room strategically to hear all the dialogues. You have all those things going on at the same time. And we got really close to the line of where too much is going on.”

That balance is hard to strike, but the sound design elicits emotions in every one of the pivotal scenes. Babcock was not immune.

“The finale, that’s just a part of the movie that every time I watch it—and it certainly happened during the sound mix part—the hairs in my arms go up,” he said. “The music, especially starting with that song, “My Idol” and going through the finale and their whole taking out Gwi-ma, just about every creative decision made there, and this includes the visuals, were all made with emotion. How is this making us feel?”

That may be why the finished product resonates.

“It’s just a really good example of how we were feeling it at the end, or how we had to make sure we were feeling it the entire time. I just think that ending is really powerful. Every decision was done with emotion.”

Babcock is also the sound designer, supervising sound editor, and re-recording mixer for the upcoming film Nuremberg, starring Russell Crowe and Rami Malek. KPop Demon Hunters airs on Netflix.