Transcript:
Schroeder sits smiling and playing the piano.
Charlie Brown and Patty stand nearby watching him. Charlie Brown asks,"Did you hear about Schreoder getting a contract with the New York Philip Harmonic?" She says,"Really?"
They walk out the room and he continues, "He's going to play Brahm's first concerto..." She asks,"Why doesn't he play Brahm's second concerto?"
He stops, spreads his hands, and replies,"Well, after all, he's only a baby!"
Original comic:
New York "Philip" Harmonic?
"Well, after all, he's only a baby!"
I wondered if that was somehow an older version of the word, but looks like it's just a joke and "philharmonic" comes from the prefix "phil-" meaning fondness for. Also, Wiktionary notes: