Fast forward to Christmas 1818 at St Nicholas Church in Oberndorf, Austria. The church's organ was damaged- some say mice damaged it, others claim is was rust- either way, the organ was not going to be operational in time for Christmas. So on Christmas Eve, Joseph Mohr went to the church's organist, local musician and schoolteacher Franz Gruber to ask him to write a melody and guitar accompaniment to his poem in order to play it that night during the midnight mass. That night, with the church lit by candles, the two men stood in front of the church and sang the hymn with guitar accompaniment. Some time later, the local man who repaired organs, familiar with the song, took a copy of the music and lyrics to his Alpine village where two well known families of singers heard it and were so impressed they included it in their holiday selections. Today the song has been translated into 300 languages and dialects all over the world.
Personally, my favorite is the German version with acoustic guitar accompaniment as it was played nearly 200 years ago in a candlelit church in the Austrian Alps.