The earlier Peanuts animated specials had marvelous jazz soundtracks by Vince Guaraldi (and later others, after Vince's passing). Not sure if jazz trio is the most obvious music to accompany cartoons, but somehow this music blended exquisitely with the characters.

Indeed from what I've read, the network was originally skeptical that jazz trio made any sense in a children's animated show, but it was remarkably successful. A couple of other tunes from the show, "Skating" and "Christmas time is here" are recognizable jazz standards to this day.

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).

Perhaps-fun stuff:

Linus and Lucy was recorded by the Vince Guaraldi Trio back in 1964.

They're all dead now, which is a shame.

But there's a brilliant modern recording, from 2016, that features the original drummer, Jerry Granelli: https://www.youtube.com/watch?v=OODA_K5hxyc

And it's definitely worth spending some time to give it a watch/listen. There's a lot more to that little tune than most people probably realize.

It's debatable whether it was first recorded in '63 or '64.

The genesis of Guaraldi's involvement was a 1963 documentary "A Boy Named Charlie Brown" which has nothing to do with the 1969 animated feature.

This was produced for TV but never aired, and recently surfaced on Youtube: https://youtu.be/UGAs5fZUvBM&t=425s

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.

It starts about twelve seconds into https://youtu.be/tcHNHRGPkkw .