In this arrangement, Pam takes the traditional Happy Birthday song and the version sung to the tune of the Merry Widow Waltz, sets both in 4/4 time and adds some do-wop for SATB quartet or choir.
In the video below, you can experiment with tempo by clicking the gear icon bottom right and changing playback speed. I think 1.25 or 1.5 might be about right.
Her original is in the key of F. My son and I recorded it lower, in D, as in the video above. Contact me for the MuseScore (open-source software) file and you can transpose it to any key that suits you.
We also made this video version for our friend Peter’s 65th birthday during the COVID-19 isolation. Same soundtrack.