Richards' final work was the mixing of eight unreleased tracks by Martha Reeves and The Vandellas for the band's 50th anniversary box set, which is to be released on 5 April.
One of the most interesting parts of this process for me was seeing how all the members of the group would work off each other -- responding and reshaping each other's words as they sang, instantaneously mixing tone and intonation to create new sounds.