"This is an oldie, but uh… well, it's an oldie where I come from."
That's Marty McFly, one of the most beloved characters in film history, referring to Chuck Berry's "Johnny B. Goode" before bringing down the house with it at his parents' high school prom. Where Marty comes from, of course, is the future, and in that scene from Back to the Future, "Johnny B. Goode" is still three years away from being released.
Yet for the crowd of students at the 1955 Enchantment Under The Sea dance in the climax of the movie, "Johnny B. Goode" IS the future -- it's the "new sound" that is going to take over America, bring the Beatles and Stones across the pond, define decades of popular culture and go mainstream before anyone expects it to. No wonder Chuck Berry's fictional cousin Marvin holds up the phone for his musical relative (at that point in his history, first cracking the charts with "Maybellene") to hear.