The knock against Mumford and Sons is that the U.K. band co-opted American roots rock and turned it into arena shoutalongs for the radio. They may not have heard the stuff until watching “O Brother Where Art Though?” but they finished six days of Austin City Limits with a roaring, populist sendoff on Sunday.

“This might be my favorite festival in the world,” singer Marcus Mumford said, before noting that it was the band’s final 2016 gig. “And you’re going to f*cking dance with us aren’t you?”

If Radiohead (a band that Mumford onstage called the greatest in the world) was an uninviting and pretentious tangle, tonight was highway cruising with respect to offering two hours of clap-ready, earnest work for, well, most people.

That includes a group of international teens, some silver-haired boomers who actually held up lighters and not smartphones, and even a cluster of men with “crew” wristbands.

Marcus Mumford was among the guests who joined Willie Nelson on stage to play “Will the Circle Be Unbroken,” at the end of Willie’s performance at The Austin City Limits Music Festival on October 9, 2016. (Tamir Kalifa for American-Statesman)

“I wish the Allman Brothers would come out,” one deadpanned beforehand. Two songs in he was singing along to “Little Lion Man.”

“That’s a lot of people, man,” Mumford said, observing the view.

For “Believe,” an ocean of patrons sung into their iPhones while simultaneously filming strangers doing the same. Like Gaspar, Balthasar, and Melchior bringing riches to baby Jesus, some apparent EDM ravers blessed the Mumford faithful by throwing glowsticks at strangers. Heal the world and all that.

Sometimes all you need are anthemic “whoa” parts, a fiddle player buried in the mix, and a trombone holding some dank whole notes in second position for several minutes. Can Mumford play with Band of Horses? Of course not, but people will respond to at-your-window romance when it has big choruses and the vulnerability of a late-night text message.

Mumford is a showman who cuts loose and stomps into adoring well-wishers like Bono. But with all the grace of a sloppy wedding where the shirt becomes unbuttoned and you’re diving in. It’s undeniable, even the reaching and handfed “With a Little Help From My Friends” Beatles cover in the style of Joe Cocker at the end. The Haim sisters spread the love, showing up to sing backup vocals on it.

And with a season-changing Samsung set, Mumford and Sons joined the all-time ranks of bands like Coldplay, Goo Goo Dolls, and Journey that write songs you listen to on desktop speakers at work, when you need a good cry.