Aha. I'm showing my age. I didn't know there was a "Peanuts" movie. I was talking about the tune "Linus and Lucy" which was the theme for the original animated TV show "A Charlie Brown Christmas."
(And I shouldn't have called it a song, as there are no words).
To complicate things further, Guaraldi released "Jazz Impressions of A Boy Named Charlie Brown" (once again, based on the 1963 documentary) but these recordings are not the same as the cues used in the documentary.
(And I shouldn't have called it a song, as there are no words).