This story makes me want to watch the movie again.
"Another of Jeff’s neighbours is the songwriter, who lives in a plush pad. He was played by an actor called Ross Bagdasarian, and he was actually a composer in real life, and made a bit of a name for himself a few years later by creating Alvin and The Chipmunks."
https://alltherightmovies.com/feature/30-interesting-facts-about-rear-window/