It was a cover of Bob ylan’s 1971 song "Watching the River Flow", and it was for a tribute album honoring Ian Stewart, the Stones' original keyboardist.

It wasn't a REAL reunion, though. Mick Jagger and Keith Richards recorded their parts in separate studios.  It's unclear if Wyman was with either of them when he laid down his part.

You can listen to the song they recorded, here:

The album, "Boogie 4 Stu", will be released NEXT Tuesday. The album is packed with blues covers. Jagger only appears on the Dylan cover, but other members of the band appear on several tracks.

Ian was a member of the band from 1962 to 1963, when he was demoted to "road manager." The Stones' manager thought that Ian should be cut because at six members, there were too many people in the band.

He also didn't think Ian fit the band's "image." Ian was kind of "burly and square-jawed." Ian accepted the demotion and continued to record and perform with the Stones up until his death in 1985.

Why don't you judge for yourself: Would Ian have fit in? Here's a picture:

Ian is the one at the far left.