On Saturday (May 25), Eric Church's Double Down Tour will come to Nashville's Nissan Stadium, in what will be a landmark date in more ways than one. Not only is it the stadium's first show featuring just one artist -- no opening act -- but it's also Church's stadium-headlining debut.

The stakes are high, but fortunately, Church has a secret weapon. Joanna Cotten, who originally signed on to tour with the country superstar as a backup singer, has become his right-hand woman, her role in his shows increasing dramatically over the past couple of years. Now, Cotten's got a legion of fans all her own, who wear her shirts and show up to Church's concerts with hand-drawn signs especially for her.

"It's a little bit shocking, right?!" Cotten says with a big, open laugh, sitting in the lobby of her Nashville hotel ahead of the Nissan Stadium performance. "Because I never expected this to turn into what it has, with Eric. I mean, some nights I'll be doing six or seven duets with him. This year, it's evolved into me doing a solo song within the set. So that's been really challenging and fun."

Cotten's role in Church's live show has grown organically over the course of the past couple years. "Last year, he would do what we called an 'audible section'. That would be something he would give us the day of the show, and he would try to wrap it around whatever city we were in," she explains. "This year, he included me in that. At first, he picked out a cover for me to do ... and then I just got in on it, and the fans responded in a good way, so we just kept it up the entire tour."

As for her newfound stardom, Cotten says that was the result of fan response, too. "They started making their own shirts, and I'd see more and more Joanna signs. So then I thought, 'Well, I better make some shirts and get my own line of merch out there, because they're doing it for me!'" she adds, cracking up.

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Her tour boss loves watching his stage serve as a platform for Cotten's rise in popularity, she goes on to say. "Eric has been so supportive of me, and it really is amazing," she relates. "I think that he thinks I didn't really get my fair shake [when I was signed as an artist to] Warner Bros. My record was never released, and I think that really gets under his skin. Because when he heard the record, he thought, 'Why has this never been heard?'"

Cotten split from that label in 2007, after recording more than 20 songs for a project that ultimately never saw the light of day.

"When I met Eric and started on tour with Eric, I was pretty much done," she recalls. "I had done everything I possibly could, and I finally just let go of it. I said, 'God, if this is something you've got for me ...' If the door was supposed to open, then I just sort of laid it down at His feet, and said, 'Open the door.' I never really thought it would look like this door!"

The singer still believes in the music she recorded back when she hoped to release an album of her own, and with the momentum of a rejuvenated fanbase behind her, she's hoping to release new material, too. In the meantime, however, she serves as Church's collaborator, even beyond the stage. Cotten was an instrumental part of creating his most recent album, Desperate Man.

"A lot of the Desperate Man record, it was me and Eric and a guitar, and that was how the songs started," she continues. "It was a really cool process. This is probably the most involved in a record I've ever been, because I was actually there. Sometimes, Eric would write the song the night before, and say 'Jo, can you meet me in the studio at one [o'clock]?' We would start with the guitar and vocals, and build from there."

That proximity to Church's career and album-making process has spurred Cotten toward returning to her own career and releasing new music, and who knows? Maybe Church will even be her backup singer one day.

"I'll ask him first!" she jokes, laughing. "He'll be my first choice."

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