Mayer was due to perform with the British trio, but first Summers had to help him tackle a song he had struggled with himself ...

Backstage footage from 2007's Live Earth benefit concert shows the Police guitarist rehearsing with Mayer and Kanye West ...

In this lesson inspired by Molly Tuttle, Trey Hensley and the O.G. of acoustic folk playing Maybelle Carter, we'll make one ...