Dave Stewart and Joss Stone debuted Superheavy's material to an unsuspecting audience at a gig venue belonging to the soul star's mother just days after they had written the tracks.
The stars have been quietly developing the supergroup - which also features Sir Mick Jagger, reggae superstar Damian Marley and Oscar-winning composer A.R. Rahman - for two years, and they went public with the band in May (11).
Stone has revealed a small crowd at her mum's Mamma Stone's venue in Exeter, south-west England were the first members of the public to hear the material.
Stone tells Britain's Daily Express, "We'd been in the studio for about three to four days and we just wrote loads of songs. Then Dave said: 'I've got an idea - let's try some of them out at your mum's place'.
"It was fun and we were totally blagging it. There was only two of us so we just bounced off each other. We wrote down the ones we thought we could pull off and just went out there and had a bit of a laugh and really enjoyed it. We hope everyone else did."