The record, which Stills forgot about soon after recording it 30 years ago, is being prepared for release by his bandmate Graham Nash.
Speaking about Stills's musical prolificacy, Nash said: "He has an enormous history of recording. In the '70s, he was a recording fool. He just found a bloody album he made with [Jimi] Hendrix."
He continued: "'Oh yeah, I forgot that.' We've got to listen to that... I want to listen to every track he ever recorded in case he recorded with Al Jolson."