"To me, Mick Jagger is one of the best blues harp players on the world," says Keith in the minute long clip. "He does things you wouldn't dream of vocally."

The Stones wrapped up the European leg of their 14 On Fire Tour at the Roskilde Festival in Denmark on July 3. The band returns to the road this fall to play Australia and New Zealand, shows that were rescheduled from this spast spring following the sudden passing of Jagger's longtime girlfriend, L'Wren Scott.