His name is Kenny Vance and he'd been with Jay & The Americans through all their hits, later turning to a career in movie music. (The story notes that the group is the only one who who opened for both The Beatles and The Stones during their first tours of North America.)

In this article from a local Florida magazine, Vance relates a great story about accidentally being mistaken for the Fab Four - and what happened when the crowd realized they weren't John, Paul, George or Ringo. 

"When we got to Washington, D.C., we hung out with [the Beatles], and we basically took a train back with them on the same car, to Penn Station in New York. And when we got there, it was like a scene out of “A Hard Day’s Night,” looking out the windows of the train. And when the door opened, there was a mob of people, [until] they said, “Oh, it’s just Jay and the Americans,” and they created a pathway, and we walked through it.  I said, “what just happened?” My god—I was a witness to history."

Kenny Vance on His Journey from the Brill Building to Boynton Beach