Country music star Billy Ray Cyrus has given rap newcomer Lil Nas X a big career boost by joining him in the studio to remix his popular track Old Town Road.

The rising hip-hop star incorporated elements of country music for the single, which was first released in December (18) and has since gone viral thanks to social media app TikTok.

Its popularity sent the tune racing up the U.S. charts, peaking at number 15 on the Billboard Hot 100 and at number 19 on the Hot Country Songs list, but chart officials recently ruled Old Town Road was not eligible for entry on Billboard's country countdown and had the track removed.

"Upon further review, it was determined that Old Town Road by Lil Nas X does not currently merit inclusion on Billboard's country charts," they shared in a statement.

The news caught the eye of Cyrus, who voiced his support for the rapper, who describes his single as "country trap," and encouraged him not to give up.

The kind words inspired Lil Nas X to invite Billy Ray into the studio to work on a remix, which dropped on Friday (05Apr19).

"I loved the song the first time I heard it," the singer told Variety in a statement. "Country music fans decide what they like. Not critics or anyone else.

"Waylon Jennings once told me every once in a while the industry outlaws someone because they're different. Country music fans don't need to be defined by critics. I've always said, don't think inside the box, don't think outside the box. Think like there is no box."

He also revealed he was "honoured to collaborate" with 19-year-old Lil Nas X, who addresses the Billboard chart controversy in the revamped tune, crooning: "Can't nobody tell me nothing, you can't tell me nothing/My life is a movie... Cowboy hat from Gucci."

Billboard bosses have yet to comment on whether the remix is now country enough to be included on the Hot Country Songs chart, but Billy Ray's daughter, pop superstar Miley, is already a big fan.

She shared a photo of the odd duo online and captioned it, "Legends supporting legends."