Rainbow Connection is from the The Muppet Movie, written by Paul Williams and Kenneth Ascher. It’s the song sung by Kermit the Frog, of course. What a sweet, gorgeous waltz it makes! I learned this tune this morning (heard it on TV last night), and here it is.
Melodeon.net’s theme of the month for January 2023, Tunes with names that start with R (working our way through the alphabet).