They're winning Grammys and selling out stadiums — how bands like Mumford & Sons and the Lumineers are leading a global phenomenon.

The future of rock & roll looks a whole lot like the past. It’s wearing vintage suspenders and playing the banjo. It’s singing high-lonesome harmonies and rediscovering Woody Guthrie. And it was all over the Grammys this month, as some of the year’s biggest bands took the stage with old-timey instruments and formal attire straight out of There Will Be Blood. Before taking Album of the Year, the night’s top prize, for their Americana-fueled barn burner Babel, British folk-rockers Mumford & Sons showed off their fingerpicking and their fedoras, stomping their weathered boots to their floorboard-rattling anthem ”I Will Wait.” Denver indie band the Lumineers strummed their ubiquitous ”Ho Hey,” while their bow-tie-clad drummer kept time with a tambourine. After picking up their Best Country Album prize, Atlanta bluegrass lovers Zac Brown Band joined Elton John, Mumford, and more for an all-star Levon Helm tribute, performing the Band’s 1968 classic ”The Weight.” For one night, at least, Hollywood felt just about as down-home as the Midnight Ramble, Helm’s legendary Woodstock jam session.

Backstage after the show, sipping from a plastic cup, Marcus Mumford celebrated his win: ”It’s f—ing awesome!” he shouted. But he wasn’t quite ready to declare a victory for folk rock just yet. ”I think it’s always been around,” he told EW. ”And you guys” — meaning Americans — ”did a good job of inventing it. The media likes to focus on things at certain times, and that’s good for us. That means we get to play lots of shows.”

That’s an understatement. Before the Grammys even aired, Mumford & Sons and the Lumineers had spent a combined 63 weeks on the Billboard 200. Babel debuted at No. 1 this past September with 600,000 copies — the biggest first-week sales for a rock band since 2008. The Lumineers’ self-titled debut climbed to No. 2, its highest spot yet, the week before the ceremony, more than 10 months after its release; both bands also saw significant post-telecast bumps in singles and album sales.

They’re hardly alone. Acoustic guitars, mandolins, and glockenspiels have slowly been taking over the charts and the radio. Last summer, American Idol winner Phillip Phillips had the most popular coronation song ever with the strummily anthemic ”Home,” a sharp departure from the show’s typical pop offerings. ”A lot of people think that ‘Home’ sounds like a Mumford & Sons record,” says Gary Trust, Billboard‘s associate director of charts and radio. ”So you’ve got another really mainstream outlet” — television — ”bringing folk to the forefront.”

In these platinum acts’ wake, lesser-known bands like Icelandic troubadours Of Monsters and Men, Seattle folk-poppers the Head and the Heart, and Brooklyn country-rock trio the Lone Bellow continue to rise. They’re not just on the radio, either. ABC’s Nashville regularly features music by rootsy artists including John Paul White (of Grammy-winning duo the Civil Wars) and Kacey Musgraves, and sets scenes in legendary local venue the Bluebird Cafe. And later this year, the Coen brothers will release Inside Llewyn Davis, their valentine to the 1960s folk scene in New York City, starring singer-actor Oscar Isaac in the title role.

Granted, most pop stars have a certain retro appeal these days. Artists such as Adele and Bruno Mars bridge the gap between young crate-diggers and their parents, who never actually stopped playing vinyl records. Acts like Jack White and the Black Keys, who’ve helped revive back-to-basics rock & roll, have also enjoyed a recent surge of Grammy recognition. Speaking to EW before the ceremony, White acknowledged the move toward all things rustic in popular music: ”I don’t know why people seem to be suddenly responding to that genre, but it’s really beautiful that people are paying attention to bands like Mumford & Sons and the Lumineers. Too many genres like jazz and blues don’t get enough attention, so it’s nice now that folk rock is. Maybe it’s cyclical.”

Folk does seem to work its way back onto the radio every 10 years or so. Many of the groups that are popular today probably grew up listening to the turn-of-the-21st-century soundtrack from O Brother, Where Art Thou?, which introduced a young audience to American roots music. But there’s also something about this new wave that distinguishes it from Gen X’s coffeehouse strumming or baby boomers’ protest music. The We’re not selling out! purism of the past is gone, as bands happily license their songs to be used in TV shows and Bing commercials. The music is less politically engaged, but more community-minded. (Quick: Which member of Of Monsters and Men is the leader? Trick question — they all are.) It’s more willing to embrace spirituality, with live shows that bring crowds together with all the lift-ev’ry-voice-and-sing fervor of a tent-revival gathering. And it reflects the larger migration toward pared-down lifestyles that started around the 2008 recession and now extends to everything from homemade fashion to artisanal food.

”These are times that were made for fires to be lit and people to gather,” says Jay ”Ketch” Secor, singer and multi-instrumentalist for the Nashville string band Old Crow Medicine Show. ”That’s what sells pickles at $7 a jar. It’s this motto: Let’s live simply. And that’s what this kind of music is, too.”

Back in 1999, long before their song ”Wagon Wheel” went platinum, Old Crow Medicine Show were spending their days busking on the streets of Boone, N.C., not feeling too optimistic about the band’s future. But on the morning after Independence Day, they decided to celebrate by playing on the street corner where their idol, the blind country legend Doc Watson, used to perform during the 1950s, right outside a pharmacy called Boone Drug. By a stroke of good luck, Watson’s daughter happened to walk by, and she was so impressed by what she heard that she brought her father over to listen. Secor will never forget his verdict: ”Boys, that was some of the most authentic old-time music I’ve heard in a long while,” he said. ”You almost got me crying.”

”We had been up all night making whiskey, and there was pills going around, so we were pretty whacked-out that morning,” Secor admits. ”But I remember it real clearly. It was like the trail opened up ahead.”

Every one of these bands seems to have a similarly dramatic origin story. Justin Vernon, the singer-songwriter behind last year’s Best New Artist winner Bon Iver, recorded his debut, For Emma Forever Ago, while living in a remote cabin in Wisconsin, where he was recovering from a bad breakup. The Lumineers began writing songs after drummer Jeremiah Fraites lost his 19-year-old brother, Josh, to a drug overdose. Singer Wesley Schultz was Josh’s best friend; to work through the grief, Schultz and Fraites started playing music together. The Lone Bellow originated as a songwriting project for singer-guitarist Zach Williams, whose wife was thrown from a horse and briefly paralyzed during their first year of marriage. (She has since recovered.) ”Living in the hospital, that’s where I started journaling, and I would write in rhyme just to help me process everything,” he says. ”And my good friends said, ‘You should learn how to play the guitar.”’

Their stories aren’t the only thing that connects them to their fans. Today you can find echoes of their organic aesthetic everywhere, from the popularity of DIY craft hub Etsy to the prevalence of farm-to-table restaurants. Secor believes that many of these values trace back to Woody Guthrie’s 1943 autobiography, Bound for Glory, in which the folk hero hopped trains across America and shacked up in hobo camps. ”I read that book when I was 18, as did a lot of people who make up this scene of roots music makers, and we all took it too literally,” he jokes. When he first started playing with Old Crow in the late ’90s, the band took hobo jaunts up to Canada and later moved to a North Carolina farmhouse, where they grew their own potatoes and made their own corn liquor. More than a decade later, Marcus Mumford would invite them on 2011’s Railroad Revival Tour, which found them all eating, sleeping, recording, and performing in vintage railcars while traveling from Oakland to New Orleans. (You can see it for yourself in last year’s well-received documentary Big Easy Express.) ”We’d play and then go back to our cars and just talk about our experiences,” Secor remembers. ”You can’t underestimate the gregariousness of this scene. It makes you want to all play together.”

There’s also that built-in post-recession appeal: ”To me, folk is about using what you have to make something,” says Lumineers bassist Ben Wahamaki. ”If you have an acoustic guitar, then you can write a song. You don’t need this pedal. You don’t need this amp. It’s that simple.”

You don’t really need a record label or a publicist, either, as long as you have a strong following online. Many of these bands are tracing the old grassroots model of building their audience crowd by crowd — while adding a very 21st-century element of viralability. That’s especially important to these groups, because even though the music feels distinctly American, it’s a global movement. ”Music is to the United States what wine is to France,” says O Brother music mastermind T Bone Burnett. ”It’s probably our most significant export…. [All of these acts] are drawing from that treasury.” There’s a reason so many budding musicians play acoustic covers of their favorite songs on YouTube, which has become its own hot spot for folk revivalists, and why so many music sites are posting unplugged performances, from NPR’s Tiny Desk Concerts to La Blogothèque’s Take Away Shows. Stripping back their music to just acoustic guitar and vocals makes for an especially intimate connection with fans, especially at a time when pop music tends to bury lead vocals under layers of production. ”We’ve gotten so far in our ability to alter [music] that it’s refreshing to see how someone actually sounds,” says Schultz.

And yet, nobody in this scene is going to swear off technology. Of Monsters and Men regularly use synthesizers; Bon Iver occasionally tweaks his vocals with Auto-Tune. Schultz says that any strict rules about instrumentation would feel too dogmatic. ”The fact that Pete Seeger didn’t want Bob Dylan to go electric doesn’t mean he shouldn’t have gone electric,” he says. (Though Dylan did stay acoustic when he performed, famously, with Mumford & Sons and the Avett Brothers on the Grammy stage in 2011.)

As a movement, it doesn’t put much stock in the star-maker machinery of pop music. Schultz points out that the Lumineers opted not to put their photo on their album cover. (In fact, Mumford & Sons are one of the few groups that appear on theirs, and it’s no coincidence that Marcus Mumford is the scene’s most recognizable face.) When the Lumineers put on a free concert in Clifton Park, N.Y., this past December, it was so packed that they went out into the parking lot to play for the people who’d been turned away, knocking on car windows, but their fans didn’t recognize them. ”They kept thinking we were trying to get tickets,” Schultz says, laughing. ”We realized that they didn’t know what we look like.” Adds Wahamaki, ”It’d be, like, a 10-second gap of silence until we were like, ‘We’re, uh, the band.”’

For the most part, though, they see that as a good thing. As Marcus Mumford told EW back in 2010, ”We became a band through a community of bands, ones that offered us shows and put us on their MySpace friends, and it was all from the fact that people weren’t exclusive. The word scene we hate very much — the idea of exclusivity, a little team, a little club that doesn’t let anyone else join them.”

The Fleet Foxes song ”Helplessness Blues” sums up this generation of folk bands pretty well. Frontman Robin Pecknold sings that he was ”raised up believing I was somehow unique/Like a snowflake distinct among snowflakes,” but now he realizes that he’d rather be ”a functioning cog in some great machinery, serving something beyond me.” Schultz says the Lumineers played their first shows at house parties, where the band and the crowd are literally on the same level, and even now that they play on stage, they still try to break down the distance between the band and the audience any way they can. For these groups, shows are all about whipping the crowd into an almost evangelical frenzy. It’s a lot like church, without the preaching. ”The contemporary Christian genre has sort of backfired,” Avett Brothers singer-guitarist Seth Avett told EW last year. ”As soon as you step up to the mic and say, ‘Here’s what you ought to believe,’ the very first thing that me or anyone that I know does is say, ‘How the hell can I get out of here?”’

Still, there are some more overt Christian undertones within the genre. Marcus Mumford’s parents are U.K. branch leaders of an evangelical church, and many of the songs on Babel are about struggles with faithfulness, both the religious and the romantic kind. Joy Williams recorded three solo albums as a Christian artist before she joined the Civil Wars, and the Lone Bellow’s Zach Williams served as the music pastor at his church.

Perhaps counterintuitively, there’s also an element of punk’s raw energy. ”We’re coming out of this in the late 20th century,” insists Secor. ”We know more about Nirvana than we do about the Skillet Lickers.” Schultz points out that Kurt Cobain called himself a folksinger, and you can hear Nirvana’s influence in the quiet-loud-quiet dynamics of many Mumford & Sons songs. Secor admits that he used to have a mohawk. ”When we were on the street corner, it was like punk rock because you gotta shout to be heard,” he says. ”We’re an old-time string band, which has this drive to it, and it’s often just one part all the way through, with some shouting in the middle, so it kind of sounds like the Sex Pistols.”

It makes sense that many of these folk-oriented bands are taking over the charts that used to be dominated by rock bands. They’re even playing the same stadiums that were once solely reserved for arena-rock groups like U2 and Coldplay. Their audience is also growing beyond the fans who might be young enough to believe that these guys invented this stuff. The Lumineers played SNL in January. Mumford & Sons just booked more dates for their Gentlemen of the Road tour, which has already led them through Ireland, Australia, and the U.S. In February, they performed two sold-out shows at the Barclays Center in Brooklyn. The first night, under glowing strings of lights, the band worked the crowd into a fury of eyes-closed, mouths-wide-open, hands-in-the-air sing-alongs. Then Marcus Mumford announced, ”We’re going to play a quiet song now” and started into a gentle version of their 2009 ballad ”Timshel.” ”You are not alone in this,” he sang softly. ”No, you are not alone in this.” Eighteen thousand fans backed him up.

Maybe Jack White is right: Everything is cyclical. During the Lumineers’ performance at New York City’s Terminal 5 in February, though, it was hard not to see how far these bands’ impact has spread. The stage was decked out with an antique console radio, dimly lit lamps, and even a coatrack. There were half-melted candles on the piano. You could almost forget that there were a few thousand people in the room — except that they were all clapping along to the group’s hit ”Ho Hey.” Singing the verses a cappella, frontman Schultz divided the crowd into two sections, pointing to one side (”Ho!”) and then the next (”Hey!”). Then he invited his surprise guests onto the stage: a dozen grade-school kids from a Success Academy in the Bronx. The whole room stood rapt, singing along — a guy in a yarmulke, a Latina girl with her boyfriend, an older blond woman with her teenage son. And the kids on stage, all dressed up in color-coordinated suits and dresses, were the loudest of them all.

Any new musical movement can go in only one of two directions: heading forward into the future or reinterpreting the past. Right now, nothing seems fresher to millennial ears than styles that were cool before their parents were even born. But this too shall pass. Everything is temporary, particularly in pop. When these Success Academy kids grow up, they’ll react against this sound by listening to something totally different. Which, ironically, will prove just how much bands like the Lumineers and Mumford & Sons left their mark on culture. And when the pendulum swings back, as it always does, another old sound will be new again.

How to be an artisanal rock star

SNL mainstay, Portlandia star, and ”wood rock” expert (see: Portlandia‘s awesome ”Dream of the 1890s”) Fred Armisen provides a playbook.

1. What to play

”You can’t go wrong with banjo or accordion. The most important thing is that the case for it is vintage and of high quality, ornate and comfy-looking, and that it has something written in cursive on it.”

2. How to travel

”In caravans of old milk-delivery trucks or newspaper trucks from, say, the ’30s. Or maybe an old city bus from 1951 in St. Louis.”

3. How to dress

”Shop for suspenders and derbies. Also, white shirts that’ve become off-white, almost sort of eggshell. And then a thick blazer helps. That goes for male or female. This is all unisex.”

4. Where to practice

”Either in a church basement or someone’s living room. If you’re in a death-metal band, you’ve got to find a warehouse somewhere. But with this kind of music, you’re okay in the living room.”

5. The ideal after-party

”I picture a late-night family picnic, and someone surprises everyone with a pie. Like, ‘Oh my gosh, guess who brought an apple-cinnamon pie!’ There’s always going to be baked goods involved.”