Cassadee Pope's "If My Heart Had a Heart" is the third single off of her sophomore album, 2018's Stages, and the first to delve into the themes of heartbreak that make up such an important part of the album. To kick off her foray into sadder subject matter, Pope brought along Dan + Shay's Shay Mooney as a backing vocalist to elevate the song's harmonies.

To learn why Pope picked Mooney -- and why it was so important to her to release "If My Heart Had a Heart" as a single -- read on.

I feel like I really set the tone with "Take You Home" and "One More Red Light" for where I am in my life, and on this new project and new phase, I didn't wanna lead with sad songs. Those were kind of the re-introductions, [letting people know that] there were gonna be songs like this on the record, and then I wanted to, [on the single I released around the album's release date], kind of hit everybody where it hurts.

[I wanted to] let everybody know that, okay, now we're gonna get into some real s--t, and it's gonna be sad for a little bit. And I wanted my next single I released to be something that I could see being a huge success, and from the first time I heard ["If My Heart Had a Heart"], I thought, "Well, this is huge."

It's such a universal feeling, and I cannot be the only person that has ever felt this way. I just had a really deep feeling that that needed to be heard.

On the demo, one of the co-writers, Josh Kerr, sang harmonies on it, and I thought that was a really nice balance. I do love when a guy sings harmonies on my stuff, because I have sort of a higher voice, and it's nice to have a balance.

This song is kind of a belter, and it's a hard song to sing. I was thinking I needed to put someone on there that can hang, or, more importantly, show off and do what they do best. So I was like, "Okay, well, that's Shay." I was really, really excited that he agreed to do it. It's not a feature; it's not a duet or anything, it just takes the song to a higher level.

Obviously this isn't just for the women out there -- this is for everybody. I feel like hearing a guy singing it with me is kind of reiterating that, that everybody can feel this way. It's not just geared towards women.