See if this page will come up for you

http://www.ingeb.org/Lieder/stillena.html

then click on 'Satz von Josef Mohr - die fruhest bekannte Melodie'

and you will hear a Silent Night you've never heard before [I bet].

The German means 'Theme by Joseph Mohr - the earliest known melody.'
-----
This site, the 'ingeb' site, is a folk blockbuster. It has so many songs, there are 9 pages for S alone. It's a good site to have in your Favorites.