My recommendations for best seldom-heard Christmas song:
Puer Natus Est Nobis. Quite possibly the most beautiful Gregorian chant ever written.
Flos Regalis. About the queen’s dental hygiene. Actually, it’s a beautiful example of early polyphony.
Lullay Lullie. You have to go back about 700 years for the original version (good records were hard to find back then). Hauntingly beautiful.
Lullay Lullie .... the Coventry Carol. I believe our church choir sings this at Christmas services. I’ll have to check out the other two.
This is a modern song that I fell in love with a couple of Christmases ago. I’d never heard of it until my niece was singing the solo part during a Christmas concert.
BarlowGirl - Hallelujah (Light Has Come)
https://www.youtube.com/watch?v=SarPJv6rUiQ