PARIS.- Stephen Fleg has been training much of his life for his Olympic moment.

Except he hasn’t. Well, not really.

Like many Olympic athletes, Fleg, known as DJ Fleg, has devoted years to perfecting his craft. But he is not an athlete in pursuit of a medal. Fleg has been tasked with creating the soundtrack for the Games’ newest and most hyped event: breaking. And that role comes with more power than you think.

Unlike gymnastics or figure skating, where performances are honed over months and sometimes years of practice, breaking lets the DJ pick the music, and competitors have to react to it. The music comes from an Olympic-approved playlist of more than 400 songs. But in each head-to-head battle, the breakers have no idea what’s coming.

“It’s very odd, feeling like we have this middle role sort of thing, but it’s a very important role,” said Fleg, who lives in the Brooklyn borough of New York City. “It’s the backbone of hip-hop and dance. There’s no dance without the music.”

Fleg, who notes that he is technically an “official” rather than a participant, is no stranger to the Games’ newest event. He started breaking as a teenager before shifting to DJ work in his late teens. Now 38, he has become a well-known figure and is frequently called on to DJ major international events including Red Bull BC One, Outbreak and recently, Olympic qualifying events.

The Paris gig, if working as a DJ at the Olympics can be considered a gig, will be a bit different thanks to its Byzantine restrictions and layers of security. There will be no fans crowding close to breakers, for example, and while the breakers will be freestyling, the DJs will be adhering to a set of restrictions.

A list of 390 songs has been cleared for use during the competition, and Fleg has 20 of his own that he is allowed to play, too. The available catalog is considered the foundation of breaking, including James Brown, 1970s funk and ’90s hip-hop.

That narrowed Olympic catalog — Fleg’s personal “primary collection” contains more than 10,000 records — will bring at least a whiff of familiarity to the choices he will make. And that is fine, he said: Fleg is much more inclined to describe breaking as an art rather than a sport. The music “is seeped into the culture,” he said. “Even if they don’t know the exact song, they should have heard it before.”

It may sound odd for someone outside the breaking world, he conceded, but he has spent hours rehearsing how to play songs for different kinds of events. Every gig is a little different, he said, and preparing for this grandest of stages has demanded a specific kind of training and organizing.

There’s a good amount of experimentation, which Fleg says “is the fun of it.” He thinks about his work from both the technical side and the artistic side. How will the beats per minute of one song correspond with the next? Should one song be slowed down, if it has the same energy to it? What if the tempo is matched but harmonically it feels a bit off?

He tried in vain to describe how he makes those decisions: shifts in vibes, a rush of endorphins, the joy painted on a breaker’s face. He relies mostly on feel, he said, and instincts honed over years of experience.

He knows what has worked before, and he knows what can lead to memorable performances. There are certain songs, for example, that will elicit a specific physical reaction from breakers if other elements of the audio are ripped away. Some may react well to a drum rhythm. Others might prefer to perform to the backdrop of a horn element.

In other less restrictive circumstances, DJs can improvise. They may enter a battle with a few ideas of how they would like to organize songs or transitions between tracks. But if a dancer reacts to something positively or negatively, DJs may shift their approach to cater to a breaker’s strengths. That spontaneity will not be on display in Paris.

At the Olympics, the rules for DJs are set and strictly enforced by the International Olympic Committee. So Fleg has practiced and submitted what he will be playing — and how — to officials before the competition, which begins Friday and ends Saturday night.

In those two days of competition, 16 B-boys and 16 B-girls, as practitioners are called, will compete head-to-head in 60-second battles. Their performances will be scored by nine judges on things like creativity, personality and technique. Those judges will use a digital slider to score each breaker to determine the winner of each matchup.

“Every breaker that’s here is improvising everything they do when it gets in that competition,” said Rynan Paguio, an assistant coach on the U.S. breaking team. “They don’t know what the DJ’s playing. They just dance to it. They don’t know what your opponent is going to do. They just react to it.”

In a sense, Fleg will be constructing the field of play in real time. The closest comparison to another Olympic sport may be surfing. Surfers don’t know what kinds of waves will appear during their heats, even if they know the contours of how they should train and the broad outlines of what they can expect.

Similarly, breakers may spend time perfecting their footwork, floor work and power moves, but they will have to react on the fly to both the music and to how their competition responds to the music. It may be the most athletic improvisation the Olympics has seen.

Expectations are high. Breaking was included in the 2018 Summer Youth Olympic Games in Buenos Aires and received rave reviews and audience numbers. That sealed the deal for its inclusion in the 2024 Games. The breaking community hopes its debut will be an accurate representation.

Now that Fleg is on the ground in Paris — he flew in from a gig in Michigan a few days ago — he’s getting himself ready, just like the Olympians who will have to perform to his soundtrack. That means laying low until the competition begins and eating some of his favorite comfort food: Japanese, Thai or Vietnamese, depending on what he can find.

Like the competitors, “I just want to do the best I can,” he said. “And my best requires me to set the other dancers up for success.”

This article originally appeared in The New York Times.