DVD and CD set features Keith Richards, John Mayer, more
April event will screen in nearly 500 locations for one-night-only showing
Run of dates to culminate in Crossroads Guitar Festival
Ron Wood, Buddy Guy, Jonny Lang combine for monster version of "Miss You"
The world's greatest ax men — including B.B. King, John Mayer and Jeff Beck — come together at the Crossroads Festival in Chicago