A key feature of every Nativity story is the exaltation expressed by the angels when they announced Jesus' birth to the shepherds on Christmas night.
The Church has even preserved their words in the Mass, when the congregation sings, "Glory to God in the Highest."
However, the Bible does not mention that the angels "sang" the Gloria. The Bible only mentions that the angels appeared to the shepherds and praised God.
And suddenly there was with the angel a multitude of the heavenly host praising God and saying,
“Glory to God in the highest,
and on earth peace among men with whom he is pleased!”
Why do we imagine that the angels were singing?
Pope Benedict XVI reflected on this detail in his homily on Christmas in 2010:
St. Luke does not say that the angels sang. He states quite soberly: the heavenly host praised God and said: “Glory to God in the highest” (Lk 2:13f.). But men have always known that the speech of angels is different from human speech, and that above all on this night of joyful proclamation it was in song that they extolled God’s heavenly glory. So this angelic song has been recognized from the earliest days as music proceeding from God, indeed, as an invitation to join in the singing with hearts filled with joy at the fact that we are loved by God.
Benedict XVI goes on to say that, "Cantare amantis est, says Saint Augustine: singing belongs to one who loves. Thus, down the centuries, the angels’ song has again and again become a song of love and joy, a song of those who love."
We imagine the angels were signing as song is proper to creatures who love God. It is inscribed in their very being.
