According to the Catholic Church, was Mary's Magnificat a spontaneous utterance?

At Luke 1: 46-55 we see Blessed Virgin Mary singing a song of praise, now known as the Magnificat, while greeting her cousin Elizabeth. I wish to know if the song of Mary was a spontaneous utterance, or was it an integration of prayers from the old Jewish scripts and the Psalms ? What do the teachings of Catholic Church say on the source(s) of the Magnificat ?