Chris Cornell meets Johnny Cash in song

The song You Never Knew My Mind is based on a break-up poem Cash wrote during his split from his first wife Vivian Liberto in 1967, but the song is strangely poignant in the wake of singer Cornell's sudden death last year.

Another track Gold All Over the Ground, performed by American country star Brad Paisley, was written in the same year for Cash's second wife June Carter.

"He (Cash) couldn't sing either of those at the time. He was still married legally to Vivian even though they were separated for a long time, but he was very much in love with my mother and he couldn't sing about those things publicly," John Carter Cash, Johnny and June's son, told AAP in Sydney.

About five years ago, Carter Cash started to look through about 2000 pieces of paper left by his father after his death in 2003.

These included biblical study notes and early drafts of some of his recorded songs, but with the help of a Cash historian he was able to whittle it down to lyrics and poetry that had never before been published or recorded.

The poetry was published in the 2016 book, Forever Words: The Unknown Poems.

Carter Cash decided to reach out to artists, including Cornell, Paisley, Kris Kristofferson, Willie Nelson, Alison Krauss, Elvis Costello and his sisters Rosanne Cash and Carlene Carter, to create songs out of this poetry for the album Johnny Cash: Forever Words.

"I met him (Cornell) backstage in the 90s at a Johnny Cash show and he told me my Dad was one of the greatest influences in his musical life," he said.

"I sent him three pieces and he chose You Never Knew My Mind."

Carter Cash produced the album alongside Steve Berkowitz (Jeff Buckley, Leonard Cohen) at The Cash Cabin Studio in Hendersonville, Tennessee.

He says there's a constant demand from Cash's fans for new material, but he's careful about what he releases from his father's collection.

*Johnny Cash: Forever Words is out now

Australian Associated Press