Most self-videoed musical performances posted on YouTube rightfully get lost in the ether, but this wasn’t the case for Swedish duo First Aid Kit. Sisters Johanna and Klara Söderberg were only 17 and 15-years-old, respectively, when they filmed themselves in the woods covering Fleet Foxes’ “Tiger Mountain Peasant Song.” The girls’ spine-tingling harmonies not only earned over four-million views, but they also stole the attention of one of their favorite bands — none other than the Fleet Foxes, who posted the flattering tribute on their MySpace page.

First Aid Kit were already successful in their home country, but that video turned them into the new darlings of the indie-folk world. “When that whole thing happened, it was really incredible for us,” Johanna tells us. “We’d released an EP in Sweden, and we’d written our own songs. But that cover got so much international attention. And we did that cover for fun — just for ourselves and our friends. We didn’t actually think they’d put it up on their MySpace profile. It was a big breakthrough for us.”

This was all in 2008, and by the end of the year, the girls had performed “Tiger Mountain Peasant Song” onstage with the Fleet Foxes, quit school, and begun touring far beyond Scandinavia. Then in 2009, they found themselves in the presence of another idol. “We’d been listening to Bright Eyes for forever,” Johanna explains. “That’s the band that got us into country and folk in the first place. We’d been huge fans, and we were able to go backstage at one of Monsters of Folk’s shows.” (Bright Eyes frontman Conor Oberst is also involved in the supergroup Monsters of Folk.)

That introduction opened even more doors. “We gave Conor our record, and then a year later he turned up at one of our shows,” Klara says. So did Jack White, who approached them about collaborating with Bright Eyes for the single “Lua” at White’s Third Man Records. First Aid Kit went on to make two records — 2012’s The Lion’s Roar and this year’s Stay Gold — with Bright Eyes’ Mike Mogus as producer. “He is one of our favorite people in the world. He is just amazing and the most incredible producer, so it’s all of these lucky breaks that we’ve had,” Klara adds. “Getting to work with the people who make the music you love, that has inspired you this much, and want to work with you — it’s indescribable how good a feeling that is.”

First Aid Kit and Oberst toured Europe together last year, and the girls contributed vocals on six tracks off his summer 2014 release, Upside Down Mountain. “We’re really, really good friends,” Klara says. “If you’d asked us when we were 13 or 14 if we were going to sing on Conor Oberst’s record, we would have like, died. It’s just so cool.”

Modern folksters may have introduced Klara and Johanna to Americana, but the sisters delved much further, getting engrossed in old country music greats. In “Emmylou,” the track that made Rolling Stone‘s Top-10 singles of 2012, the band’s love for June Carter, Johnny Cash, and Emmylou Harris is apparent. First-time listeners of the Swedish outfit could easily mistake their affected-but-convincing country twangs for honest-to-goodness Southern accents. No wonder they’re so comfortable when they tour around these parts.

“It just has a different vibe than anywhere else in the world,” Johanna says. “It feels like we’re at home. Even though we’re not from here, we just feel like we fit in. The crowds are loud, in a good way. You get more of a response. I think it’s special because our music is so inspired by American culture. We felt like it could go either way, but people really appreciate our take on it. We offer a new perspective, I think.”

Like everywhere else, America has certainly latched onto the magic of First Aid Kit. With harmonies powerful enough to bring Patti Smith to tears (that happened, by the way), their inexplicably beautiful music is the kind you want to get lost in the mountains with — and that’s pretty much how they prefer to create their music. “I can see us going into a cabin in the woods or something. We just long for writing sometimes, but I think it can be anywhere — kind of like isolating yourself a little bit to a place where you can get close to your emotions,” Johanna says.

The sisters write songs together, drawing inspiration from things like love, life’s big questions, and poetry. Take the title track to the new album, “Stay Gold.” It pulls words from Robert Frost’s “No Gold Can Stay.” Klara says, “The song had started actually before we’d read the poem. We were thinking about it, and the element ‘gold’ was already in the words, but then I was just kind of stuck in the song, not knowing what to do next.

“And I had this collection of poetry,” she continues. “I was going through it, and I just happened upon this page with ‘Nothing Gold Can Stay’ by Robert Frost. I read it and thought, ‘Oh my God. This is exactly what we’re trying to say.'”

The first single released off Stay Gold, “My Silver Lining,” is a personal song for the sisters. They sing, “I try not to hold on to what is gone/ I try to do right what is wrong/ I try to keep on keeping on.” The song is all about how intensely they’ve lived thus far, going from schoolgirls to folk stars. “We’d been wondering what to do next, and that song is about struggling with your place in the world,” Johanna says. “It’s very basic, human sort of emotions. But it’s like a mantra for ourselves — don’t take the easy road just because something seems like the best solution. It may not be the right one.”