Kacey Musgraves and Katy Perry's friendship evolved into a 14-show tour together, with the country star joining Perry's Prismatic run. But they're not just sharing a stage -- the two singers are also writing together, and recently collaborated on a track that was inspired by ... the Wizard of Oz?!

"I brought some ideas, and we actually ended up writing a pretty cool song," Musgraves tells Billboard. "It's loosely based on Dorothy's version of 'The Wizard of Oz,' her being in love with the Tin Man, but he didn't have a heart. And hopefully maybe something will happen with it down the road. Either way, it's cool to step out of my zone and write for somebody else."

Ever since Perry tweeted her love for Musgraves' 'Merry Go 'Round' hit and the pair appeared on 'CMT Crossroads' together -- mashing their pop and country influences into a colorful wonderland -- fans have been excited about the pairing of the quirky and super talented stars.

Musgraves' stint on the road with Perry kicked off Sunday (Aug. 10), and while she's excited for the opportunity, it's not just for her benefit. "It's going to be really interesting and really good for me, I believe, 'cause there are a lot of people who would probably never have heard country music otherwise," says the singer. "So I'm proud to be an ambassador, and if I pick up some new fans along the way, I think that's great. I think with Katy, with her music and style, anything goes, and I think if people are just coming to hear great music and have a great time, it'll make sense."

If fans put on their ruby-red slippers and click their heels three times, maybe they'll treat us to a sneak peek of this 'Oz'-some song they're working on! See what we did there?

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