Father Mullady in Homiletic & Pastoral Review responds to a readers query...
http://www.hprweb.com/2017/03/questions-answered-51/
I added a comment, below the column (if the moderator lets it be posted).
Regarding "Mary, did you know?" Almost from the first time I heard it sung I "heard" Our Lady say, "Yes," to each query., And, the song touches me each time the choir sings it "correctly" (according to my standard).Is this a mystical experience? No, rather it is an interpretation, a kind of expansion of meaning, flowing logically from the Scriptures and the Church's doctrine regarding Mary's fiat and her pondering in her heart (Luke 2:19, 52) what to expect from her son.Written by an Evangelical, the song seems to me to be an unconscious bridge from the Evangelical Protestant to orthodox Catholicism. Is there any other contemporary Christian song that articulates so much of which the Church teaches about Mary?