The story goes as follows: Joseph Mohr, a priest at Gruber’s St Nicholas parish church, showed Gruber a six-stanza poem he’d written in 1816. Gruber was so impressed that he set it to music in 1818. That same year, the two men sang Stille Nacht for the first time at Christmas Mass, while Mohr played guitar and the choir repeated the last two lines of each verse (the church organ had broken down!). The version sung by Bing Crosby in 1935 is the fourth best-selling single of all-time.