How ‘KPop Demon Hunters’ Created the Year’s Biggest K-pop Hits

In the world of KPop Demon Hunters, K-pop is a battleground for hearts, minds and souls. And for superpowered girl group HUNTR/X, who face off against their demon rivals Saja Boys, they mostly fight with really good pop songs.

To bring this soundtrack — from the fizzy confection “Soda Pop” to fierce girl crush anthem “Takedown” — to life, it took a village of real K-pop hitmakers: musicians from THEBLACKLABEL, founded by BLACKPINK producer Teddy Park, crafted beats, while the songwriting credits are filled top-to-bottom with names that K-pop fans will recognize. 

“In film musicals, you are often hiring people who specialize in narrative writing,” executive music producer Ian Eisendrath, known for his work on film and Broadway musicals, tells Billboard. “This was interesting because it was sort of the opposite. It was bringing in people from the pop world to write for the film, as opposed to people from the film world to write in the style of K-pop.”

In this fictional universe, both the demon slayers and baddie boyband dominate the charts (even leaving TWICE, who cameo on the soundtrack, in their dust) — so the music ideally had to stand alone as crowd-pleasing pop songs. Maybe that’s why, in our world, too, the two groups have been going up, up, up: the album has risen to No. 2 on the Billboard 200, while HUNTR/X and Saja Boys have flown past IRL peers on the Spotify charts. 

So, how did they fit these specific story beats inside universal pop songs? Korean-American songwriter and vocalist EJAE (who provides the singing voice of Rumi) helped thread that needle on “How It’s Done,” “Golden” and “Your Idol.” “We can all relate to characters, whether they’re superheroes or not,” she says — though she has more in common with the leading HUNTR/X ladies than most. A former K-pop trainee of almost a decade, EJAE, like half-demon Rumi, knows “how it feels having to hide your insecurities.”

“‘Golden’ is a song that I put all my experience into, what I wanted to hear when I was training, because it’s not an easy industry,” she continues. “It’s very competitive. Being perfect is such a big thing while training. So that part, feeling so broken inside, me not aligning and getting dropped, was part of it too. I brought that heartbreak I felt into the lyrics and when I’m singing.”

As with her previous work for some of K-pop’s biggest girl groups (Red Velvet, aespa, NMIXX), songwriting was a team effort; EJAE bounced lyrics back and forth with Mark Sonnenblick, a composer with a background in narrative songwriting. But, whereas many of the writers on the project were used to cranking out demos in fast-paced environments like K-pop songwriting camps, this process was far more iterative — some songs took years to finalize.

“There were a lot of revisions that we wouldn’t typically make for a human artist,” says Stephen Kirk, who is known for producing BTS chart-toppers “Butter” and “Permission to Dance” alongside partner Jenna Andrews. Soaring ballad “Free” came easily for the duo — but the emotional thrust of finale “What It Sounds Like” was harder to nail down. “That was a totally different adventure,” Andrews says. “I think I counted 147 different revisions,” adds Kirk.

An early reference was Lorde’s “Green Light,” though Kirk and Andrews’ first draft, which headed “super in the direction” of the 2017 Melodrama single, was handily rejected by the studio. “They were like, ‘No, definitely not,’” Kirk laughs. But building off of existing K-pop bangers allowed the global squad to “get on the same page,” Eisendrath says. “We wanted them to do their version, but it helped us, even across language barriers, really communicate what we were going for.”

Below, Eisendrath tells Billboard how he got KPop Demon Hunter’s “stable” of talent to speak the same musical language — and create the year’s biggest K-pop hits in the process. 

How familiar were you with K-pop before working on KPop Demon Hunters?

When BTS came on the scene is when I got into K-pop. I was just sort of immediately struck by the theatricality of it. I feel like K-pop, like a Broadway musical or a film score, has so much going on, so many layers, and there’s such energy and drama to it. I’d always thought it would be amazing to somehow utilize this musical language for narrative function. I just also think K-pop is so well-produced. Everything about the music production to the mix and the mastering — I’ve always been incredibly impressed and excited about that aesthetic.

How did you get brought on to the project?

[President of Sony Pictures Music Group] Spring Aspers called me in fall of ‘22 and said, “We have this incredible new film, early days, it’s going to be a K-pop, music-driven project. THEBLACKLABEL is on board to write songs, but they’re going to need a lot of support in terms of how to make these songs filmic. Also, the directors and producer really need someone to develop musical language, and to figure out how to fit the songs into the narrative.’” So nothing really existed at that point.

I read that while the film was in development, certain songs were temped in. Were those existing K-pop songs?

A lot of it was real K-pop songs. Maggie Kang, one of our directors, grew up steeped in K-pop. That was such a gift for this process because, not only is she a great filmmaker, but she came to it as an absolute lover of this genre of music. So it was really fun to work with her, Chris [Appelhans] and Michelle Wong, our producer, to develop references for every song. We would often have five to 10 references for every song. Sometimes it was, “Hey, check out this group. We really love the drums, the groove here. We love the production colors here.”

I do think, when working with writers outside of film, and from the music industry, references are the absolute clearest way for us all to get on the same page. And what was great was that no one went and just did the reference. We didn’t want that.

Tell me about that team of writers.

We had six to seven writers that we could task with different songs, some even with sections of songs, different elements. Some people wrote the topline and lyrics. Others created music production. We even brought in someone who specialized in more of a theater narrative lyric. Working with all those writers, I think, is what made this have this crazy alchemy. The number of writers on this film definitely exceeds the number of songwriters on most film musical projects — often it’s two people or one person. 

We had the whole team at THEBLACKLABEL, including Teddy [Park], 24, Soulscape, Danny Chung. We had EJAE, who, early on, created the demos and helped us find the sound of HUNTR/X and she ended up writing top line and lyrics for a lot of songs. We had Steven Kirk and Jenna Andrews of [BTS’] “Butter” and “Dynamite” fame, who wrote two of the songs. Lindgren wrote “Takedown,” and then Mark Sonnenblick we brought in to collaborate on lyrics focusing on story and character. We also used people top of the field in K-pop to mix and master the songs.

How would you describe the sound THEBLACKLABEL brought to the soundtrack? When I listened to “How It’s Done” for the first time, I could immediately hear Teddy Park in the production.

It’s totally a THEBLACKLABEL drop, right? It has the hard-hitting beat. It has this incredible synth lead line. We wanted to have a drop like that for “How It’s Done.” THEBLACKLABEL has that all over their work — it’s in BLACKPINK and other songs all the time. We wanted to make sure HUNTR/X had that, so we created space. That might not happen in a normal narrative song, where all they say [on the chorus] is “how it’s done, done, done.” But that’s a THEBLACKLABEL signature. There are definitely BLACKPINK vibes in the score, though I also feel like they did their own thing for us.

How was this process different for the songwriters who are used to K-pop songwriting camps?

We spent about three years working on these songs. The first year was spent beating out what these songs needed to be, for story, for character, for music, vibe and how that all fits together. Because you’re not just thinking of a song, you’re thinking of a musical arc for the whole film. So that work was going on one side, then on the other side, it was figuring out how we can all work together in the way that all of these writers work best. And it was actually a really gratifying process, because we all had to learn how to speak each other’s language. 

Because animation is able to be developed very organically, we had to just keep iterating on the songs. I know that was an experience that all the songwriters both enjoyed and became exhausted by. We didn’t stop until everyone was happy.

There’s a mix of English and Korean in the songs. Was that always the plan? Was there ever a discussion to make the songs solely in English?

It happens all the time in K-pop songs, and we all loved that. The bulk of the writers on these songs are Korean, and it was really important that we were honoring and centering the film on that culture. There was never really any blowback, and that was always the goal, like, let’s interpolate both languages as much as possible. Often, we would lean towards English on the things that, if the audience didn’t understand this, then they wouldn’t understand the film. Some stuff just sounded amazing in Korean and some stuff sounded amazing in English. [It] was sort of like, “What’s the most appealing flavor?”

How did TWICE come to be involved with the soundtrack? 

Dana [Sano, from Republic Records,] and Spring really went on a quest to figure out who our partner should be. TWICE was their first choice, and they opened up that relationship and made the collaboration possible. We were all just so thrilled that they wanted to do it. Not only are we obsessed with them as a group and their music, but they’re also just so in the center of K-pop right now. It felt authenticating when they wanted to be part of this. Like, “Phew, we are creating songs that these K-pop groups feel are K-pop songs they want to perform.”

There’s a moment in the film where the Saja Boys are introduced and EXO’s “Love Me Right” plays. Then there’s this great K-drama spoof moment with “Love, Maybe” by MeloMance, originally from the Business Proposal soundtrack.

Maggie and Chris wanted something everybody knew — the EXO — when the Saja Boys appeared, then to go to that K-drama easter egg moment where they fall in love. That was in the film before I worked on it. There are those things that are evergreen, that never go away because you just can’t imagine them not being there. 

I was very nervous about that, though. Chris and Maggie remember, I was like, “Oh, I don’t know if we should do that, because we can’t steal away from whatever the Saja Boys sing.” Looking back, I think it was just real fear. Like, how are you going to beat the EXO song? But I do feel the three work well and the first two build to “Soda Pop” in such a satisfying way.

The response to this film has been incredible. Were you surprised to see the music take off on the charts? 

Totally. I’ve loved these songs, and I think all the people who worked on them have loved them, but you just never know how something’s going to do. I’ve worked on films I thought were going to be mega hits and they weren’t, and others that I thought weren’t going to be and were. It’s so thrilling that people are hearing the songs in two ways. Some are loving the film, and the film is making the songs hits, and then some people are just encountering the songs, and the songs are making the film hit.

Why do you think it’s connecting with audiences so well?

On one hand, people who love and know K-pop are loving these songs because they are new K-pop songs, right? I think they’re also responding visually to the film and feeling like, “Yeah, I’ve been to a concert like that. Yes, I know a girl group like that. I know a K-pop idol like that.” They know this world, and it’s feeling authentic and true to them.

And then I think there are a ton of people who probably wouldn’t have encountered K-pop had they not seen the film, and they are so drawn to the story and the characters. The film impacts them on an emotional level, whether it’s excitement, or deep ache, or being moved at the end when Rumi finally finds her voice.

Netflix is planning to submit “Golden” for Oscars consideration. How does that make you feel?

That’s really gratifying because, out of any song in the film, that one had the most [options] written for that spot. It took a long, long time to find. It was literally the last song that we locked up, [we were] creating a new bridge for it in December and recording in January. What I’m excited about is that it’s doing it all. It’s a K-pop song, it’s a performance song, and then it’s got an internal monologue in the middle of it all. And people are just loving and embracing it as a pop song.