SANTA ROSA, Calif. — In a “Peanuts” strip from the mid-1950s, Charlie Brown walks through the first panel and finds Schroeder sitting in front of an adult-size hi-fi, his ear to the speaker. “Shh,” Schroeder says, “I’m listening to Beethoven’s Ninth.” Charlie Brown inspects Schroeder’s outfit. “In an overcoat?” he asks. Schroeder leans even closer to the speaker and responds, “The first movement was so beautiful it gave me the chills!”

In the world of “Peanuts,” of course, Schroeder was the Beethoven-obsessed music nerd who lost patience when Lucy interrupted his practice and who called time-outs as a baseball catcher to share composer trivia with the pitcher. Yet musicologists and art curators have learned that there was much more than a punch line to Charles Schulz’s invocation of Beethoven’s music.

“If you don’t read music and you can’t identify the music in the strips, then you lose out on some of the meaning,” said William Meredith, the director of the Ira F. Brilliant Center for Beethoven Studies at San Jose State University, who has studied hundreds of Beethoven-themed “Peanuts” strips.

When Schroeder pounded on his piano, his eyes clenched in a trance, the notes floating above his head were no random ink spots dropped into the key of G. Schulz carefully chose each snatch of music he drew and transcribed the notes from the score. More than an illustration, the music was a soundtrack to the strip, introducing the characters’ state of emotion, prompting one of them to ask a question or punctuating an interaction.