Country music legend Johnny Cash was so prolific in his final years there are still five albums' worth of new material in the vaults, according to his producer son.

John Carter Cash claims he has discovered tons of unreleased recordings by his late father while archiving his work following his death 11 years ago (03).

And he insists there are enough outtakes from Cash's American Recordings sessions with producer Rick Rubin to fill another multi-disc box set.

He tells Britain's The Guardian newspaper, "There are a few things that are in the works right now, probably four or five albums if we wanted to release everything. There may be three or four albums' worth of American Recordings stuff, but some of it may never see the light of day."

Cash's lost 1980s album, Out Among the Stars, was released this week (beg24Mar14).