Khalid’s smash debut album, American Teen, launched the artist—who turned twenty just a few months ago—to superstar status with lightning speed. It peaked at number four on the Billboard 200 chart, earned him a slew of Grammy nominations, and made him an arena-sized headliner coming straight out of Americas High School in El Paso.

It also made him a sought-after collaborator for artists looking for someone with a pure, rich vocal tone to lend them a hook or a duet partner. While Khalid hasn’t announced any plans for his follow-up to American Teen—he told Texas Monthly in March that “I’m not gonna lie to you and say I have an album ready—I don’t“—many artists have tapped his talents on tracks of their own. In fact, he’s done so many collaborations that his guest appearances could approximate an entire album. Or a playlist.

Some of Khalid’s 2018 collaborations are with superstars: Kendrick Lamar makes an uncredited appearance on “The Ways,” a song from the Black Panther soundtrack Khalid recorded with Swae Lee; Khalid brings the hook to “OTW” featuring Ty Dolla $ign and fellow fresh-faced singer 6lack; his steamy duet with singer Normani got a Rick Ross remix in June. On each of those cuts, there’s a low-key, organic element that makes it feel like the rappers are meeting Khalid on his own turf.

Aside from being tapped by vets like Ross and Lamar, a lot of Khalid’s collaborations are with similarly young artists who are building out their nascent careers. He joined 21-year-old singer H.E.R. on “The Way” from the Superfly soundtrack, an R&B jam built around a vampy bassline that feels like less of a pop tune than anything on American Teen. He partnered with 22-year-old Dutch DJ/super-producer Martin Garrix on the ballad “Ocean” in June, and teamed up with 19-year-old Canadian phenom Shawn Mendes for the simple, acoustic-guitar driven duet “Youth” the same month. “Lovely,” his collaboration with 16-year-old singer Billie Eilish, is an appropriately-titled piece of chamber-pop melancholy built around minor-key piano, strings, and an ethereal combination of their voices. On the just-released non-album single “Eastside” from producer Benny Blanco, Khalid’s voice pairs up with 22-year-old pop sensation Halsey. He also teamed back up with production duo DJDS, with whom he collaborated last year, for the song “No Pain,” alongside Charlie Wilson and Charlotte Day Wilson.

While these tracks don’t have the singular vision of American Teen, there’s a cohesive feel to them—which is surprising for a set of songs on which Khalid was often utilized as a color in someone else’s musical palette, rather than as the painter himself. People who are looking to work with Khalid seem interested in hearing him alongside pianos and acoustic guitars playing minor-key melodies, and using his voice to do emotional heavy-lifting. That’s a far cry from some of the summery pop on American Teen, but part of that album’s appeal was that its focus on youth—on songs like the title track, “Young, Dumb, and Broke,” and “8TEEN”—felt more weighty because of the singer’s awareness that youth is fleeting. His breakthrough album is mostly a sunny one on the surface, but his songs have always had a melancholy edge. The nine tracks he’s recorded in collaboration with other artists so far in 2018 suggest that other artists have recognized that wistfulness, and listening to them as a sort-of bootleg follow-up to American Teen gives us an alternate glimpse of Khalid, one where the moody side of the artist is in the forefront.