A demo song from about 1979 featuring Ronnie James Dio's vocals could be an unreleased Black Sabbath song. The demo was released by the stepson of late Black Sabbath keyboardist Geoff Nicholls. The believed title is "Slapback," and it was included on a cassette tape that featured other material recorded by the band while they were prepping for their then next album, which was 1980's Heaven And Hell.
Nicholls' stepson, Gary Rees, uploaded the song to YouTube. In the description he said, “It doesn't sound like a typical Sabbath song, if it is them, but it does sound like Ronnie James Dio. I have no idea about anything; I wasn't there. Everything is speculation.”
He also said that he has several more tapes to explore, but his vintage equipment needed to be serviced and there was “no spare cash” to cover the costs. Rees asked that people donate to a Patreon fund so he could continue this work.