"The Dominicans were not unaware that, at certain times, so eloquent of the beauty of God was the celebration of the Divine Office that it itself became a 'holy preaching'. Thus, with regard to the Salve Regina, for example, which the Dominicans sang every night after Compline, Jordan of Saxony remarks: "How many people have been brought to tears of devotion by this holy praise...!' And he adds that, on a number of occasions, while the brethren were singing out the line from the Salve, 'Turn then most gracious advocate', one of the brothers had a vision of the Mother of God. He saw her, Jordan reports, 'prostrating herself in the presence of her Son and praying for the safety of the whole Order.'"
-from p. 39-40, The New Wine of Dominican Spirituality: A Drink Called Happiness, by Fr. Paul Murray OP