After mouse-headed dance music superstar Deadmau5 topped off last year’s Summer Set Music & Camping Festival with a hi-fi set that rivaled the new “Star Wars” movie in visual pizazz, the fest turned to the only other EDM producer/DJ to grace the cover of Rolling Stone magazine in recent years as its big wow of a closing act Sunday.

Raven-haired, black-bespectacled Los Angeles partystarter Skrillex lately has headlined such top-tier music fests as Lollapalooza and Coachella, but at Somerset Amphitheater’s fifth annual psychedelic camp-out, he brought out about 18,000 attendees, fewer than at last year’s finale.

That was one of several signs of the hyper party vibe being toned down this year at Summer Set, a year that looked as if organizers struggled to keep the lineup fresh after five years. The festival’s third-day aesthetic always is a bit ragged, but Sunday looked especially grungy.

Used glow sticks, leftover confetti and oodles of cigarette butts littered the festival grounds when campers rolled out of their tents early (2:30 p.m.) to catch the first few acts of the day. The prior day’s lineup relied heavily on indie-rap stars, including Chance the Rapper. There was a fairly avid reception for Baltimore area hip-hop smoothie Logic on Sunday as well, but the EDM acts drew the bigger responses from the throngs of shirtless and/or bikini-clad teens and 20-somethings.

One thing that hasn’t changed after five years: The Summer Set crowd seems eternally young, and relatively diverse, too.

Bloomington-reared party-bro rapper Mod Sun kicked off the main-stage lineup in front of a modestly sized and mildly interested crowd, his hyper wild-boy songs seemingly adding salt to the two-day hangover wounds. Things were even more mellow and meager over on the large, valley-shaped Grove stage area, where Minneapolis DJ Guggenz spun out appropriately chilled-out, soulful grooves to a few dozen fans mostly watching from up the hill seated in the scant shade.

The festival finally started waking up in the all-shaded Big Top Tent. Perhaps the most Boulder-y music act to ever hail from Boulder, Colo., the trio SunSquabi gradually sparked the crowd into dance mode with slow-building funk jams played live on guitar, bass and drums but set to prerecorded synths and electronic beats.

DJ Mustard, of the Los Angeles hip-hop scene, also woke things up on the big stage with a turntable set heavily geared toward arena rap concerts and short attention spans. The quick-changing song snippets included everything from hits he’s produced for Big Sean and Trey Songz to Oasis’ “Wonderwall.”

The most curious wonder of Sunday’s lineup was DJ Marshmello, a new alter ego of Philadelphia electronic star Dotcom, who wears a big marshmallow-shaped head much like Deadmau5. He similarly didn’t seem to have an original thought going through his music Sunday, melding ultra-whirry, high-wired dubstep-circa-2013 with suburbanite club remixes by A$AP Ferg and Dillon Francis. The crowd ate him up like he was sandwiched between chocolate and graham crackers on Sunday, though, the dance party in front of the stage suddenly turning into a carnivalistic explosion that lasted a full hour.

Marshmello went over so big, in fact, Skrillex might have fizzled by comparison. For that matter, he also earned a run for his money from Gramatik, the day’s last act on the Grove stage. The Slovenia-reared producer packed the valley floor in front of the stage and crammed ample, cool samples of old-school funk, blues and jazz music into his classic house-flavored beats. No costume head required.

Still, there was no mistaking who the star du jour was once the sun set and the entire crowd erupted to the loud, opening whir that announced the real-life Sonny Moore’s arrival. His first-ever festival appearance in our area was a lot like his last local gig at First Avenue on a rare club tour in 2013 in pacing. He really never let up on his onslaught of rib-cage-rattling beats — a contrast to last year’s gradually mellowing Deadmau5 finale. There’s really just one button Skrillex presses at his shows: on.

He did mix in more remix snippets and more mainstream, sing-songy mash-ups this time, dropping in everything from Kiss, Weezer and Queen to Pusha T and a new version of Galantis’ “No Money.” How new? “I just remixed this one on the plane coming out here,” he told the crowd beforehand, about the only time he broke from his nonstop “let me feel you!” party-sparking banter.

Summer Set organizers and the neon-equipped fans also rose to the occasion of Skrillex’s overdue appearance, supplying enough smoke, flashing/spinning lights and sheer volume for an equally hyperactive stage production. Even the cows around Somerset may have felt a little woozy and strung-out after this one.