I’m not sure what I think the most beautiful song I’ve ever heard is, but I know my mind usually goes to two songs:

Pastoral, by a man who went by the name of Moondog. He was a legendary blind composer, playing on the streets of New York City between the late '40s through to the early '70s.

He’s kind of a “your favorite musician’s favorite musician’s favorite musician” figure, and was known to play several instruments of his own invention (one of which I believe is used in this song, but I’m not sure). This is a very minimal song, but beauty doesn’t always demand grandeur.

Second would be Slips Away by Peter Silberman, the lead singer of a band called The Antlers (who also have a bunch of really moving tracks in their discography).

This one is also very simple, and quite melancholy, but I think it says all that needs saying. If I have a funeral when I pass, I’d really like this to be played at it.