Sturgill Simpson and Jason Isbell shared the stage at a recent show in Tuscaloosa, Ala., for a duet version of Terry Allen's "Amarillo Highway."

The two Americana artists were scheduled to play a show together, along with Brandy Clark, at the Tuscaloosa Amphitheater on Oct. 15, but they surprised concertgoers with a special joint performance of "Amarillo Highway." Their version of the song, which was released on Allen's 1979 album Lubbock (on Everything), takes the classic country duet and moves it into slightly more serious territory, both lyrically and musically.

Simpson and Isbell swapped lead vocals during the first half of the track before Isbell took over the show, along with guitarist Laur Joamets. Press play on the video above to watch the performance.

While Isbell and Simpson have shared many bills over the years, they hadn't performed onstage together before "Amarillo Highway," and they've never officially toured together. Fans can only hope that this duet is a sign of things to come.

Both artists are set to appear at Nashville's Mother Church, the Ryman Auditorium, in October. Isbell is scheduled to play Oct. 23-26, and Simpson will perform Oct. 30-Nov. 1.