Sheck Wes performs Saturday at the Trillectro festival at Merriweather Post Pavilion in Columbia, Md. (Kyle Gustafson for The Washington Post)
Pop music critic

Summer was over, but everybody still had “Mo Bamba” on the brain. All the young dudes kept singing it in the concession line. Over near the entrance — where the music was still a faraway slurry of echoes and bass — a girl grabbed her friend’s arm as though she’d seen a ghost: “I think I hear ‘Mo Bamba!’ ”

Did she? Was this really happening? Did 10,000 teenage musos really come to this day-long music festival just to hear one song?

The festival was Trillectro, a resurgent grass-rooted mega-concert staged at Merriweather Post Pavilion on Saturday; the song was, of course, “Mo Bamba,” a jammed-down-your-throat summer jam from the shouty young Harlem rapper Sheck Wes. So when he finally materialized to recite it at dusk, it sounded like the most important ditty in the world — a declaration of existence from a 20-year-old who’s grown furious with life but still feels overjoyed to be living it. And after three minutes of this blunt-force bliss, it was over and done. Much of the crowd instantly dispersed in big numbers, like poof, leaving poor Sheck Wes to roar the rest of his rhymes into a half-empty field.

Rapper Playboi Carti hits the festival stage. (Kyle Gustafson for The Washington Post)

Texan rapper Maxo Kream performs on the second stage at Trillectro. (Kyle Gustafson for The Washington Post)

In that bewildering moment, and in others, Trillectro surfaced the eerie disconnect between reality and the digital plane, where the video for “Mo Bamba” has been viewed more than 15 million times on YouTube. Isn’t there more to absorb from a three-dimensional Sheck Wes performance than mere confirmation of a hit song’s physical existence? And shouldn’t there have been more YouTube habitués in attendance at Trillectro to do that absorbing?

The number of empty seats at this festival certainly felt disproportionate to the exceptional talents onstage. And while that could have been a mood crusher, it wasn’t.

SZA’s headlining set felt big-hearted and lighthearted — she belts to big crowds like she’s singing into her hairbrush. Houston rapper Maxo Kream told hard-knock survival stories with so much buoyancy that he never had a chance to feel sorry for himself. Playboi Carti teased his rhymes in a halting stop-and-go style that was more stop than go. Young Thug rapped in a sweet-and-sour spritz that was more sour than sweet. There was a lot to hear and a lot to love.

Rapper Rico Nasty, a Maryland native, performs at Merriweather Post Pavilion. (Kyle Gustafson for The Washington Post)

But the festival’s most auspicious music came from Rico Nasty, an already larger-than-life rookie from Maryland who changes her hairstyle as frequently as the rest of us change our underwear. At Trillectro, her tresses were a glorious green, the color of Scope mouthwash, and her rapping was playfully pugnacious, blurring frenzy and fun.

Between joyful sneers, Nasty encouraged her audience to “rage” — and Miami’s Smokepurpp followed her set by giving the exact same instructions, urging the crowd to commit their bodies to his brawny, ear-bullying music.

Like nearly every vocalist at Trillectro, he frequently pointed his microphone upward and outward, asking fans to finish his couplets — a tactic that used to feel like a life hack for the out-of-breath but nowadays feels increasingly significant. You probably discovered these songs on the airless Internet, but now it’s your job to complete them in real life.