This is actually strictly dialogue between Barry and his grandfather, Joe, made circa 1951 or right around that time. They were at a "Record Your Own Voice" booth, and this is approximately how the conversation went

JOE: All right! "A Happy Birthday," come on, go ahead, sing
BARRY: What? What?
JOE: Sing. I have the words for you, sing it. Sing it. Sing to me! "A happy birthday to you."
BARRY: N-no, I can't! I have to go to the bathroom
JOE: All right, go ahead, Barry, sing it, sing it! Sing it! Go ahead
BARRY: When?
JOE: I said now. Go ahead, sing it. "Happy." Go ahead, come on. Come on, sing it! Come on, go ahead
BARRY: How?
JOE: Like this, "Happy." Come on, go ahead. All right, my dear grandson, "A Happy Birthday." Barry's gonna sing to you a nice song. Go ahead, Barry, sing it! Go ahead, sing it! Come on, come on, Barry, sing it! Sing "A Happy Birthday." Barry, don't you want to sing it? Come on, Barry, sing it. Well, I'm sorry, my dear grandson, Barry, don't want to sing for you. OK, what do you want to sing? Do you want to sing a rhumba? All right, sing the rhumba. Go ahead, Barry, sing it! Go ahead, Barry, sing it! Go ahead, Barry. Come on, sing it. Come on, Barry! You gotta talk to make a record. Don't you want to make a record? Don't you want to make a record? You want to make a record, Barry? Huh? Go ahead!