Bong Joon-ho and his Parasite composer struggled to perfect the film’s key song

Every element of Bong Joon-ho’s Parasite is perfectly calibrated, from the performances to the sets to the music. The most incredible part of the score is a track that runs more than seven minutes long: “The Belt of Faith,” which plays alongside a key sequence in the film. (Incidentally, it was also Parasite’s Oscar-night music.)

As the Kim family, who are struggling to make ends meet, slowly infiltrate the rich Park household, they weaponize what the Park matriarch calls “the belt of faith” — the Kims recommend each other for jobs with the Parks, who trust their recommendations, rather than gambling on hiring through a service or open interview. The track accompanies the Kim family’s coup de grace in taking advantage of that so-called belt.

“It is version 7 or 9 that you are listening to,” composer Jung Jae-il told Polygon via email. Despite how many emotions the track was meant to contain — and how many people and situations it was juggling — Jung said director Bong wanted the score to express just one texture with concentrated sounds. “Music could be the railway,” Jung explained, “and the drama, actors, and situations could be the chain of trains.”

The difficulty in following that mandate was in avoiding just following the stories playing out on screen. Instead, Jung was tasked with carrying them along smoothly, “like a bullet train.” Jung says he had thought one of his previous versions of the song was perfect, but it didn’t meet Bong’s satisfaction. “I drank so much that night with despair,” he says. “The next morning, I crawled to the piano and started improvising meaningless phrases, and that led me to the final version you are listening to.” (In an earlier interview with Polygon, director Bong recalled that the struggle to get “The Belt of Faith” just right made him fear that Jung would never work with him again.)

For the overall sound of the film, Bong told Jung he wanted to find the right “sound texture” that would run throughout the film, and mentioned strings as a key element. “He said he listened to Handel and Vivaldi, who is the symbol of Baroque [music], while he was writing the script,” Jung said.

But the reliance on strings created its own difficulties. “Strings are especially difficult to express with computers,” Jung says, explaining that his composing process involved first sitting down with Bong to discuss where the music was meant to go, then composing on the computer and letting Bong listen. If Bong liked what he was hearing, the next step was orchestrating and recording the music. If he didn’t, Jung would re-write.

Other pieces of Parasite’s score were less difficult, such as “Zappaguri.” That track, which plays like a compressed version of “The Belt of Faith,” comes during a sequence where the Kims struggle to meet a tight deadline, with each family member juggling a separate stressful task. “The approach was totally different from ‘The Belt of Faith,’” Jung says. “I wanted it to function in the style of a Tom & Jerry piece,” emphasizing each beat of the action rather than flowing through like “The Belt of Faith.” That process was much smoother: “Mr. Bong liked it the first time.”

Parasite is streaming on Hulu now.

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