"Peanuts". Here's a video about a 2009 exhibit of these Beethoven strips from the Ira F. Brilliant Center for Beethoven Studies, King Library, San José State University:
Since then I've discovered quite alot of Beethoven/Peanuts cartoons on YT. I'm not sure how involved Mr. Schulz was with the cartoons, but this excerpt of Schroeder playing (and imagining?) the 2nd movement Adagio Cantabile from Beethoven's "Pathetique" Sonata Op.13. - is just great:
Peanuts: Schroeder plays Piano Sonata No. 8 Sonata Pathétique
Here, Lucy "vocalizes" to the Moonlight Sonata:
"Schroeder" from "You're a Good Man, Charlie Brown!"