To sing with us, 1) Click on the music thumbnail icon to view the sheet music (you don't have to read music!), and 2) Engage the audio file by clicking on the Real audio or Mp3 file.
Recently found and authenticated, this document was written by Joseph Mohr. In it he acknowledges the poem was written in 1816, and also that Franz Gruber wrote the melody - "Melodie von Fr. Xav. Gruber."
This is assumed to be similar to the version that the two men sang with guitar accompaniment at the Christmas Eve service in 1818.