Já me tinha lembrado disto no ano passado e este ano concretizei. A música é uma interpretação de Sufjan Stevens de "Once In Royal David's City".
Aqui fica um pequeno historial da canção e outras versões para quem estiver interessado:
"The words to the carol Once in Royal Davids city were written by Mrs. C.F. Alexander ( 1818 - 1895 ) and makes wonderful use of the English language to paint a picture of the events of the nativity. Mrs. Alexander wrote many poems for children, chiefly on religious subjects and was the wife of the Bishop of Derry. The music to Once in Royal Davids city was composed by H.J. Gauntlett. This carol is believed to have first been published in the early nineteenth century."

Outra versão:
youtube.com/watch?v=1RC34N1TfCQ