Corrected entry: When Marty begins playing "Johnny B. Goode", the guitar tone is suddenly distorted whereas it was clean in the prior song without him ever adjusting the amp or the guitar's volume knob. The guitar also becomes more distorted during the guitar solo.
MasterOfAll
17th Feb 2012
Correction: Turning a knob on a guitar takes almost no time at all. He could have easily turned it between shots, or when his back was turned toward the camera.
MasterOfAll