For her upcoming album with good friend Rodney CrowellEmmylou Harris says that that the duo is keeping it simple.

"It's just me and Rodney singing," she tells Rolling Stone. "I don't know how different that will be. We're actually working with Joe Henry to produce. We wanted to change things up just a little bit, but basically it's just two friends singing together."

Harris and Crowell have been tight-lipped about what fans can expect from the project, which is a followup to their 2013 collaboration, 'Old Yellow Moon.' The two songwriters have been working together since Crowell joined Harris' Hot Band in 1975.

“We just decided to do another duet album together, to have some more fun,” Crowell says. “We had a ball working on ‘Old Yellow Moon.’ We bring out a lot of good stuff in each other. We just understood that we have to have more time to explore that.”

One song that may appear on the album is an unnamed tune that they began close to two decades ago.

“Right now, Emmy and I are collaborating on one song that I started to write 17, 18 years ago,” Crowell says. “I’m no good at telling a song what it should be. It will tell me what it wants to be.”

Harris will be honored with a star-studded tribute concert, 'The Life & Songs of Emmylou Harris,' featuring Crowell, Martina McBrideSheryl Crow and many more, in January.