The discovery of letters involving two icons of American music-Johnny Cash and Ray Charles-has led to the release of a "lost" duet the two recorded nearly 30 years ago.

"Why Me, Lord?," written by Kris Kristofferson, was recorded by Cash and Charles in 1981 but never released. It now appears on "Rare Genius: The Undiscovered Masters," a new collection of Ray Charles tracks arriving Oct. 26 on Concord Records.

Two letters Cash wrote to Charles were discovered last May by Ray Charles Foundation president Valerie Ervin. She was in the midst of reviewing material archived at the Los Angeles-based Ray Charles Memorial Library for the recent BIO Channel documentary "Ray Charles America."

"I am so proud when I tell people that I have recorded a song with you," begins Cash's first letter to Charles dated Dec. 11, 1981. "I hope you like this tape. I realize that the orchestration isn't big and I don't sing very good, but I think the thing has a feeling and a quality that the fans would really enjoy. I would like to release it as a single on CBS, with your permission, on an equal royalty share basis. Would this be acceptable to you?"

It was. However, for reasons that remain unclear, the gospel-flavored pairing-with Cash taking lead vocals and Charles delivering soulful backup-was never released. A second letter from Cash identified the song's title and Billy Sherrill as its producer. But where was the tape?

"I never knew that Ray Charles and Johnny Cash recorded together prior to 1984's 'Friendship' album when they dueted on 'Crazy Old Soldier,' " Ray Charles Marketing Group president Tony Gumina says.

Following the letters' discovery, Gumina called Margie Hunt, who was a staffer at Columbia in the early '80s. Hunt in turn reached out to Marty Stuart, who confirmed he had played guitar on the session for Cash's 1981 album "The Baron." Hunt then suggested Gumina contact recording engineer Al Quaglieri, who confirmed the unreleased track was part of those sessions. The master tape was found last June at a storage facility in New York.

"This song has seen the light of day," Gumina says, "and the music world is better off because of that."