Rascal Flatts + Lauren Alaina = a match made in heaven.

The American Idol alum features on the band's new album, Back to Us, out May 19, partnering on a soaring, heart-tugging duet, "Are You Happy Now." Only ET has your first listen to the track with the exclusive premiere -- press play, below!

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"It's hard to look down the list of female singers and pick one that can go toe-to-toe with Gary [LeVox] in the studio," Jay DeMarcus tells ET.

The song was originally written for Rascal Flatt's 2014 album, Rewind, alongside songwriter Sean McConnell, but it took three years to find the right partner to sing on it.

"Gary’s got one of those rare abilities to have an extraordinary range, vocally, sing all kinds of vocal chops and make it sound like it was spontaneous in the first time he’s ever done it, and that’s hard to do for a singer to have all of those gifts, and all of those chops and still make it feel authentic and make it feel like he’s tied to the message of the song," he continues. "A lot of people can show off with their range and vocal chops. Very few can do that and project emotion at the same time. And Gary and Lauren Alaina can absolutely do that. Lauren came in and was thrilled to be a part of the project and just sang her rear end off. She really did."

The project was a full-circle moment for Alaina, who covered "God Bless the Broken Road" in middle school. "My 11-year-old self is doing the happiest of happy dances," she jokes.

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"I love this song, I love the message, I love the lyrics and the beautiful melodies," she says. "We have all had our hearts broken at some point. 'Are You Happy Now' takes the heartbreak and turns it into something really powerful. It’s about the other side of heartbreak when you realize the person who walked away regrets it and you’re saying, 'I told you so.'"

According to LeVox, the band is relishing a new level of creative freedom on Back to Us, which also features contributions from Chris Stapleton and Shay Mooney.

"We're really excited about this release," he says. "There is something freeing about being in a position where we don’t have anything to prove anymore. We can really follow where the road takes us and the thing that brought us together, which is our unique camaraderie."