The Gospel of Luke is the one that gives us the most information about the birth of Jesus. It is also the only one which includes what we’ve come to refer to as “the four nativity songs” or “canticles:” those of Mary (1:46-55), Zechariah (1:68-79), the angels (2:14), and Simeon (2:29-32). These have each come to be known by the opening Latin words in the 5th century Vulgate: Mary’s “Magnificat,” Zechariah’s “Benedictus,” the angels’ “Gloria,” and Simeon’s “Nunc Dimittis.” We call them songs, even though the Bible simply says these words were spoken. But their lyrical, poetic style lends validity to our traditional description of them as songs. If that is so, then they were probably “sung” in a style similar to chant, as were also the Psalms.
In each of these four, we can’t help but wonder how Luke knew about them: the circumstances of their initial utterance, and the text of what was said/sung. He does tell us in the introduction in the opening verses that he had examined what others had written as well as interviewing witnesses. That leads to the very likely conclusion that all four of these accounts came from Luke’s having talked with Mary, listening to and recording her memories. Of course, all this occurred under the inspiration of the Holy Spirit, ensuring that we have the record as God’s own revelation. According to some ancient traditions, Mary spent the latter years of her life in Ephesus under the loving care of the Apostle John, as directed by Jesus in one of His “Seven Last Words from the Cross” (John 19:26-27). Perhaps Luke interviewed her there at some point.