Father Joseph Mohr had written a poem "Stille Nacht! Heilige Nacht" prior to his transfer to St Nicholas' Church in Oberndorf, Austria. This poem was to become the words of the carol "Silent Night". Silent Night's melody was written by Mohr's friend Franz Gruber, an accomplished organist at St Nicholas' Church. Mohr had requested Gruber to write a melody and guitar accompaniment for the words of his poem. Gruber's breathtakingly beautiful tune provided the perfect match for Mohr's words. According to "Christmas historian" Bill Egan, on Christmas Eve of 1818, Mohr and Gruber sang the carol at Christmas Mass in St Nicholas' Church with Mohr playing his guitar and the choir repeating the last two lines of each verse. The tale that the organ at the Church had broken down, thus necessitating the use of a guitar, is now generally held to be a myth.
Here is a new guitar arrangement of "Silent Night" written by Glenn Jarrett, together with printable PDF version. Standard arrangements for piano and other instruments can be accessed here: Silent Night (piano).