An engraving of an angel with the words Gloria in excelsis Deo et in terra pax ("Glory to God in the highest and peace on Earth"), the words angels sang when the birth of Christ was announced to shepherds, as recounted in Luke 2:14. This formed the basis of a doxology which is today known as Gloria in Excelsis Deo. A tradition recorded in the Liber Pontificalis states that Pope Telesphorus used the hymn at the Mass of Christmas Day in the 2nd century A.D., and it is still recited in its entirety in the Byzantine Rite Orthros service. The Gloria has been and still is sung to a wide variety of melodies, modern scholars having catalogued well over two hundred of them.Image: Dalziel Brothers, after J. R. Clayton