‘Play On Mr Music,’ by the Upsetter Revue featuring the Heptones, the Congos and Junior Murvin, has long been the Holy Grail for roots reggae connoisseurs—a song often dreamt of, but never gaining an official release, until now. The result of an impromptu studio jam, captured on celluloid for Jeremy Marre’s Roots Rock Reggae documentary in May 1977, the track celebrates the undeniable pull of Perry’s musical artistry, with both musicians and onlookers enhanced by the uplifting qualities of a spliff. With the Heptones’ rousing harmony given extra depth by backing from the Congos, the rhythm is given its melodic anchor by bassist and bandleader Boris Gardiner.