AceShowbiz - Rapper Lil Nas X and Billy Ray Cyrus teamed up on Sunday, April 28, to perform their smash hit "Old Town Road" for the very first time at California country festival Stagecoach.

The young star was heavily rumoured to be joining the veteran country singer onstage at the annual bash, and they didn't disappoint when closing night DJ Diplo invited the unlikely couple onstage during his set.

"It's been the number one song for weeks - and it's a country song!" the superstar DJ exclaimed as he introduced the pair to the cheering crowds.

The track was initially snubbed by the leading country radio networks until Billy Ray stepped in and added his vocals to what the experts considered a rap track.

It wasn't the only surprise Diplo had in store for fans - in addition to performing with singers Sam Hunt and Cam, he also released his official remix of "Old Town Road" immediately after Lil Nas X's live debut of the viral track.

After the show, Cyrus took to Twitter to share a snap of himself and Lil Nas X online.

"Theres (sic) only 1 horse missing in this photo!" he captioned the image. "Thank you @diplo for having us! What an incredible night! @LilNasX #oldtownroad #stagecoach".

The rapper also posted video footage of their appearance online, and simply wrote, "THANK YOU STAGECOACH!!!"

Lil Nas X has since been given another reason to celebrate - "Old Town Road" scored a fourth week at the top of America's Billboard Hot 100 chart on Monday.

The popularity of the unlikely Cyrus collaboration helps Lil Nas X score the longest-leading number one debut as a lead artist since OMI dominated the Hot 100 in 2015 with his "Cheerleader" smash - that track held on to the top spot for a total of six weeks.

"Old Town Road" keeps Post Malone's Wow at two, while the white rap star also occupies third place with "Sunflower (Spider-Man: Into the Spider-Verse)", featuring Swae Lee. Ariana Grande's "7 Rings" holds steady at four, and the Jonas Brothers round out the new top five with "Sucker".