Getting into the spirit of a music fest meant to double as an artists gathering, Mavis Staples told the crowd at the Eaux Claires Music & Art Festival on Saturday afternoon how happy she was to finally congregate with an artist who wrote a song on her last record.

“I just met Justin Bon Iver backstage,” the gospel/soul legend said, referring to festival founder and Eau Claire’s own Grammy-winning indie-rock hero Justin Vernon. “I forgot to ask if he was available.”

For at least the foreseeable future, Vernon might be wed to his hometown’s namesake festival. The second installment of Eaux Claires — which took place Friday and Saturday in fields overlooking the Chippewa River — maintained the buzz from its inaugural year with an overflow of good vibes and great collaborations.

Between the near-perfect 80-degree weather on Saturday, the moderately short concession lines and all the festival’s extra gimmicks and artsy touches, most of Eaux Claires’ 20,000 attendees worked their smile muscles as hard as they did their calves. The latter were tested going up and down the hill and through the woods to get to all of the event’s seven stages.

Some of the extra do-dads in between the stages included a large church organ in the middle of a field and a random, lit-up hole in the ground for people to look down. (Sample reaction: “I think it’s where Justin pours his bong water.”) Oh fer fun.

Many of the musicians appeared to be having as merry a time as the crowd. Year Two offered even more of the artistic mix-and-match and push-and-pull that Vernon pushed for in Eaux Claires’ inaugural year.

After performing his long-awaited new Bon Iver album “22, A Million” in its entirety Friday — and announcing its Sept. 30 release date afterward — Vernon let loose Saturday and regularly popped up in other people’s sets. His itinerary included: a tight and lively Southern music revue led by his buddy Phil Cook of Megafaun; a loose and mixed-bag all-star tribute to the Grateful Dead anchored by Eaux Claires co-curator Aaron Dessner and his bandmates in the National, plus a finale by electro-pop act Francis and the Lights in one of the big hilltop tents.

That last appearance, for the aptly named hit “Friends,” also featured a surprise guest spot by Chicago’s new breakout star Chance the Rapper, who performed a day earlier at the nearby Summer Set Festival.

Chance may have put in fewer miles getting there Saturday than Jess Wolfe and Holly Laessig covered just bouncing between appearances on the festival grounds. The visually and vocally harmonious singers of Lucius also showed up in matching cloaks and haircuts to sing with Staples, Jenny Lewis and the Day of the Dead tribute band.

“We look like triplets,” Staples deadpanned as Wolfe and Laessig added to a devilish cover of the Talking Heads classic “Slippery People.” The Lucius singers were less effective, however, singing “Uncle John’s Band” in the Dead tribute, one of many in that set to offer off-key harmonizing and sparkless grooves (at least one trait of which does not befit a true Dead set).

Lewis gave the most commanding performance of the day. Decked out in a white hemp-leaf-adorned Nudie suit, the former Rilo Kiley singer confidently strummed and strutted her way through the solo tunes “Just One of the Boys” and “She’s Not Me” and enlisted the Staves and Lucius for a divine “Rise Up With Fists.”

“Something just happens when you sing with people like that,” a beaming Lewis said.

Both Staples and Lewis were unhappy about sound troubles. Production is still an area where the fledgling festival could improve. The worst example came when visionary soul/R&B singer Erykah Badu took the stage 40 minutes late — not cool, but not exactly a shocker. Organizers cut off Badu’s first regional performance in almost a decade after about 50 minutes, just as she was hitting her groove with “Love of My Life” and “Tyrone.” Fine, but why let 20 minutes of downtime pass before Nathaniel Rateliff & the Night Sweats took the opposite stage?

As they did at recent Rock the Garden concerts in Minneapolis, both Rateliff and Lucius proved lively and accessibly charming enough Saturday to play to the most mainstream festival crowds. No way could the same be said of some of the other highlights of the day.

Grunge/punk vets the Melvins, for instance, filled a hilltop tent with 10 minutes of thundering instrumental noise and then launched into a spastic version of Kiss’ “Deuce.” Los Angeles newcomer Moses Sumney earned a rave response in the next tent over with a hazy, mellow-cool blend of electro-soul and R&B falsetto that was part Bon Iver and part Sam Cooke.

Weirdest and best of all, rising neo-classical ensemble yMusic performed Sufjan Stevens and Son Lux songs behind a mesh video scrim in an enclosed, air-conditioned tent where the music all came through headphones (no amplification). Maybe the good folks at Orchestra Hall can learn a thing or two from Eaux Claires, just like rock festival organizers everywhere.


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