How it was that two years later the poem should be set to music is the stuff of romantic legend:
One popular version of the story is that on Christmas Eve in 1818, the organ at the Church of St. Nicholas was broken—perhaps due to rust, or perhaps because mice had eaten through the bellows. With no organ to accompany the music at the Christmas liturgy, Father Mohr asked his good friend, parish organist Nicholas Gruber, to write a setting for the poem which could be sung a cappella, without instrumental accompaniment.
There are no official records in Oberndorf to verify the “broken organ” story. What is clear is that on Christmas Eve 1818, Father Mohr, with the Christmas poem tucked in his pocket, trudged through the snow to Gruber's home. While the priest waited, Gruber quickly composed a musical score. Mohr and Gruber would sing the melody, and the choir would join in. Instead of the customary organ accompaniment, there would be a guitar solo played by Father Mohr.
Years later, Gruber would write about the night when the now-famous song was hastily completed: “On the very same evening,” Gruber wrote,
“...I fulfilled the musical curate's request and [the] simple composition was immediately performed on the holy night to the acclaim of everyone present.”
Silent Night Spreads Around the World
The following year, in 1819, the master organ builder Karl Mauracher came to the Church of St. Nicholas to work on the organ. It's believed that when he returned to his home in the Zillertal, near Innsbruck, Mauracher took with him a copy of “Silent Night.” Mauracher seems to have shared the song with two musical families: the Rainers and the Strassers.
On Christmas Eve 1819, the Rainers sang the song in their parish church in Fügen. Three years later, they performed it for Tsar Alexander I of Russia and Emperor Franz I of Austria. In 1839 they brought the hymn to the United States, performing Silent Night in German at the Alexander Hamilton Monument outside of New York's Trinity Church.
The Strassers were Austrian glovemakers but also enjoyed singing. The family traveled each year to German fairs, selling their gloves and entertaining shoppers with song. The Strasser sisters helped to spread the song throughout northern Europe, singing at outdoor fairs. In 1834, they were invited to perform Silent Night for King Frederick William IV of Prussia. The king ordered his cathedral choir to sing it every Christmas eve, establishing a new tradition.
In 1863, nearly fifty years after the song was written in German, Silent Night was translated into English. That English version was first printed in 1871, in the Sunday School Hymnalpublished by Rev. Dr. Charles L. Hutchins, rector of Grace Church in Medford, Massachusetts. Today the familiar lyrics of Silent Night are sung in more than 300 languages around the world.
Who Was Father Mohr?
There was nothing to suggest, when Josef Mohr was born in 1792, that he would one day compose what is perhaps the world's most beloved Christmas song. His mother, Anna Schoiberen, was a poor embroiderer, and Josef was the third child she had borne out of wedlock. His father Franz Mohr was a mercenary soldier in the army of the prince-archbishop of Salzburg, and abandoned Josef's mother before he was born.
Just hours after his birth on December 11, 1792, Josef was baptized in Salzburg's Baroque Cathedral of Saint Rupert and Saint Vergilius—in the same baptismal font in which composer Wolfgang Amadeus Mozart had been baptized thirty-five years earlier.  As was customary at the time, since his parents were unmarried, he received his given name from his baptismal godfather Josef Wohlmuth, who served as Salzburg's last executioner. Wohlmuth did not himself attend the baptism, but was represented at the ceremony by Franziska Zachin.
Given the circumstances of his birth, young Josef might have simply remained in poverty. But fortunately for Josef, the vicar and leader of music at Salzburg Cathedral, Johann Nepomuk Hiernle, took him under his wing. Hiernle nurtured Josef's musical talent and encouraged him to get an education. Even as a young boy, Joseph Mohr served as a singer and violinist in the choir of the University Church and at the Benedictine monastery church of St. Peter. At sixteen, he began studies at the Benedictine monastery of Kremsmünster, in the province of Upper Austria. Two years later, he returned to Salzburg to attend the Lyceum school.
Josef felt a strong pull to the priesthood; but in those days, his illegitimate birth made it necessary for him to obtain a special dispensation before he could attend seminary. Permission was finally granted and in 1811, he entered the seminary. Four years later—on August 21, 1815—Josef Mohr graduated and was ordained as a priest.
Father Mohr served at a number of parishes throughout Austria. He was a generous man who donated most of his salary to charity. In the Alpine village of Wagrain, he established a scholarship fund to allow children from poor families to attend school, and he set up a system for the care of the elderly. He died at the age of 55 of pulmonary disease, and is buried in the cemetery at Wagrain.
In Austria, his hymn Stille Nacht is considered a national treasure. Traditionally, the song may not be played publicly before Christmas Eve.