Gillian Welch and David Rawlings lend their stellar harmonies to Barry Gibb for “Butterfly,” a track off Gibb’s forthcoming country/roots album Greenfields, produced by Dave Cobb.

The song was first released as a deep track on the 1970 Bee Gees outtakes compilation Inception/Nostalgia. Written by Barry, Maurice, and Robin Gibb, it was cut by the British group United 4 + 2 in 1967, three years before the Bee Gees released their own version.

Greenfields, due January 8th, features collaborations with artists as varied as Keith Urban, Brandi Carlile, Dolly Parton and Olivia Newton-John. Last month, Gibb offered a preview of the album with “Words of a Fool,” a duet with Jason Isbell.

“From the first day we stepped into RCA Studios in Nashville… the album took on a life of its own,” Gibb said in a statement. “I feel deep down that Maurice and Robin would have loved this album for different reasons. I wish we could have all been together to do it…but I think we were.”

An upcoming documentary on the story of the Bee Gees, How Can You Mend a Broken Heart, premieres Saturday on HBO. Welch and Rawlings, meanwhile, have been releasing their lost-songs project Boots throughout 2020. A physical box-set collection of the songs is out now.