Can you believe there are unreleased Bob Dylan/Johnny Cash duets out there in the world? Well, there are. Dylan and Cash, two of the all-time great icons of American music, were friends and mutual admirers, and they liked playing music together, but we don’t have too much record of it. Dylan and Cash famously teamed up on “Girl From The North Country,” a song from Dylan’s 1969 album Nashville Skyline, and they sang a few songs together when Cash invited Dylan onto a 1969 episode of The Johnny Cash Show, but that’s pretty much been it. Apparently, though, the two recorded an entire session together in 1969, and we’ll soon get to hear it.

Rolling Stone reports that the next edition of Dylan’s archival Bootleg Series will devote a disc and a half to the Cash/Dylan session. The two apparently recorded this thing one day with the rockabilly legend Carl Perkins, and it features the two of them playing each other’s songs and also doing standards like “Mystery Train,” “You Are My Sunshine,” and a handful of tracks from country originator Jimmie Rodgers.

The three-CD collection Bob Dylan (Featuring Johnny Cash) — Travelin’ Thru, 1967–1969: The Bootleg Series Vol. 15 is coming out this fall, and it also features outtakes from the Dylan albums John Wesley Harding and Nashville Skyline. The focus on this set seems to be Dylan’s love of country music. Beyond those outtakes and the Cash session, it’ll also feature some Johnny Cash covers that Dylan recorded for 1970’s Self Portrait, the full soundtrack of Dylan’s appearance on The Johnny Cash Show, and a few home recordings that Dylan did in 1970 with the bluegrass great Earl Scruggs.

Also, one of the songs from the Cash session is “Wanted Man,” which Dylan and Cash co-wrote during the session. A week later, Cash played the song live at San Quentin prison and included it on his Live At San Quentin album. Apparently, on the sessions, you can hear June Carter Cash in the background, making suggestions. A Dylan source tells Rolling Stone, “Every time Carl Perkins takes a solo, Johnny Cash says, ‘Carl Perkins, everybody!’ It’s so cool… They are just singing Jimmie Rodgers song off the top of their heads. Johnny starts, Bob joins in. It’s just two guys relaxing in the studio and having fun. That’s what we tried to focus on. We wanted to focus on the fun they were having.”

The Dylan archivists have shared two tracks so far, neither of which features Cash. The first is an alternate take on the John Wesley Harding song “I Pity The Poor Immigrant.” Here it is:

And the second is a different take on “Tell Me That It Isn’t True,” from Nashville Skyline:

Bob Dylan (Featuring Johnny Cash) — Travelin’ Thru, 1967–1969: The Bootleg Series Vol. 15 is out 11/1, and you can see the tracklist at Rolling Stone.