“Shellback was bored,” ILYA says, reflecting on how he and the Swedish hit-maker ended up working together for the first time — ultimately changing the course of his career. Having grown up in what he calls “the hood of Sweden,” ILYA’s discovery of music production was a bit of a surprise — quite literally, as he found a CD of the music-making program Dance eJay in a cereal box. From there, he says, he “fell in love with creating.”

By his late teens, in 2005, ILYA signed a publishing deal with Warner Chappell Music and remembers “grinding, grinding, grinding… with not a lot happening.” Several years later, he met Shellback (Britney Spears, P!nk, Taylor Swift), who eventually asked ILYA what he was working on, and later suggested to his close collaborator Max Martin that they should all team up. “Coming up to that point, I had a lot of almosts,” recalls ILYA, now 37. “I had songs with One Direction that just fell off and didn’t make the albums. All those years were so important to learn how to act in the room, how to deal with people’s emotions and all these things leading up to when I got the shot from Shellback and Max.”

Almost immediately, ILYA scored a major win as a co-producer and co-writer on Ariana Grande and Iggy Azalea’s 2014 smash, “Problem,” which hit No. 2 on the Billboard Hot 100. “Every time I make music today, I try to channel the energy I had when we did ‘Problem,’ ” says ILYA, who has continued his relationship with Grande for a decade, leading into her current era. “Making that beat, it was like, ‘I’m just going to do me.’ And when that success finally happened… It was unbelievable.”

Ariana Grande, “Yes, And?”

“This whole song was her idea — she had a vision. I remember we were going through chords and she was like, ‘It needs to be more confident. It has to be more sassy.’ When Ari’s describing an emotion she wants to have, I instantly go, ‘What sounds can make that emotion come to life?’ And to me, the 909 drums are what that vibe is. In the bridge there are all these funny Mellotron sounds that are really ’60s, Beatles-esque, and a flute that Max played that I laugh at every time I hear it. Once we finished it, that’s when I fell in love with it.”

Tate McRae, “Guilty Conscience”

“The first time I worked with [Tate] she seemed very unsure of everything. There was one song we did so many versions of because she couldn’t decide which one was the best. But I think growing up, she feels much more confident in what she likes, which helps me a lot. I’ve never finished a song as fast as this one… it was all her initiative. We wrote it and then had to turn it in that week or the week after. Everything [came] from whatever happened that day.”

Conan Gray, “Never Ending Song”

“Conan started working with Max for a few days and they cracked this sonic direction, but not the details. And then Max came to me and was like, ‘Conan would love to work with you for this next round.’ Once the song was done, [Max and I] spent a lot of time running stuff through analog gear. Sometimes it’s cool if a song sounds like it’s made quickly — but the details and tasteful stuff that you can get from analog gear, you can’t beat that.”

This story will appear in the Jan. 27, 2024, issue of Billboard.