Henry Gauntlett’s melody for “Once in Royal David’s City” is called “Irby.”
The carol began as a poem by Cecil Frances Alexander, first published in 1848 in her collection Hymns for Little Children. The poem retells the Nativity for children and illustrates the Christian belief that Jesus was “born of the Virgin Mary.”
English organist and composer Henry John Gauntlett set the poem to music in 1849. His tune “Irby” became the standard melody associated with the carol, although the words and tune have separate origins and dates.
The tune gained an especially famous performance tradition through the Festival of Nine Lessons and Carols at King’s College Chapel, Cambridge. Since 1919, the Christmas Eve service has traditionally begun with “Once in Royal David’s City,” often with the first verse sung by a boy chorister as a solo.