via the Beethoven sequence from A Boy Named Charlie Brown (1969, dir. Bill Melendez), which can be seen here.
"The centerpiece of the film from a visual standpoint is the scene where Schroeder plays Beethoven’s sonata Pathetique. We are treated to an extraordinary visual collage which borders on the psychedelic, a collage which aptly suggests how music might really come alive inside the creative mind.
The swirling colors, quick glimpses of real locations and personalities, and heady rhythmic editing all make for a rather breathtaking sequence, reminding one that, although largely forgotten now, A Boy Named Charlie Brown was considered a popular “head film” of its day. This sequence alone certainly suggests that the film might have been enjoyed by anyone of a certain higher mind, along with films such as Yellow Submarine.” (via)