This article originally appeared at Billboard.

A cryptic 13-second Facebook video from Zac Brown has circulated in recent weeks, with dancers, horns and glitter teasing an “epic,” one-night-only event at Denver’s 1st Bank Center Aug. 7. The show is free — but only a friend can get you in the door.

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It’s all part of Zac Brown’s latest project with his other band, the electronic outfit Sir Rosevelt, and their collaboration with Montreal-based theatrical pioneers, Cirque du Soleil, with fans themselves distributing all the tickets.

Brown kicked off the initiative June 21, by distributing free tickets to just a handful of followers, who were then instructed to keep one ticket for themselves and share three additional ticket codes with friends who were important in their lives. Those fans, too, received extra tickets to pass along exponentially until 5,000 tickets were released. Fans can track the ticketing in real time and are being asked to post personal stories on the platform explaining why they shared their tickets with the people they did.

As with his pioneering eat-n-greets years ago on ZBB tours, Brown is looking to extend a level of “hospitality” to concert-goers not often seen in the business. “We’re just digging deeper into a network of people who are passionate about the same things,” Brown tells Billboard. “It’s a new way to connect.”

Presenting the pay-it-forward promo are Brown and partner Enterprise Holdings, parent company of Enterprise Rent-A-Car. Enterprise vp marketing Frank Thurman said the partnership with Sir Rosevelt is about “acts of kindness and creating unique connections.” “We’re able to reward those fans who are picking people up,” Thurman said — a play on the rental car company’s longtime catchphrase “we’ll pick you up.”

This will be just the second U.S. performance ever by Sir Rosevelt, after shows in London, Australia, and last year at the Cosmopolitan resort in Las Vegas. Brown says rehearsals have been underway for a while, with Cirque producers creating entirely new theatrics specifically for his event. No word yet on whether it will tour, but the circus aspect is “woven throughout the concert,” Brown says. “We’re definitely gonna open some doors.

“I’ve always wanted to work with them,” he says of Cirque du Soleil. “It’s not that different than what we do as musicians. It’s talented people working together on a common goal.”

He likens the gymnasts, acrobats, flame-throwers and others who perform Cirque’s feats of derring-do to Olympians and other performers “who have dedicated their lives to doing one thing, and really mastered it. I’ve always liked their approach, their costumes, the make-up, and that there is no limit to what can happen on stage.”

Sir Rosevelt, formed in 2016, also features singer-songwriter Niko Moon and producer Ben Simonetti. The band’s sound is typically classified as EDM-pop — a different universe than ZBB’s usual turf — but Brown says he’d rather not label it.

“There are electronic elements for sure,” he says of Rosevelt’s groove. “It’s got live instrumentation, and we can go places sonically, add a little more swagger . . . but I don’t know what you’d really call it without limiting it.”