It is a lovely piece with a beautiful dialog between two distinct voices: Mary and Joseph on one hand, and Jesus on the other, with the break in dialogue at the full bar. The contrast between the very plain question (Son, why hast thou done so to us? Thy father and I have sought thee sorrowing) and the answer from Jesus is musically striking.
The range of the answer is the most notable aspect. It is higher and more intense than the affectionate but mundane opening. I'm especially struck by the difference between the two renderings of the word father here. Initially we have a very plain "pater" with a simple rhythm. But when Jesus speaks, he references "quae Patris mei" and the chant assumes its most melismatic posture, soaring high and holding, as if to underscore the special character of this father in question.
The structure allows us to put ourselves in the role of the parents and feel the deep puzzlement they must have felt at this announcement. Namely: Your father is looking for you; I'm out doing my father's work.
What a dialogue! It is beautifully captured here, this familial conversation, one that begins in a conventional way with parents wondering where the child is, but ends in the most astonishing way, with a reference to the seemingly impossible and the very miracle of his life. So the very meaning of Holy Family takes on the deepest possible significance: the parent's sorrow for the missing son turns to awe as the son speaks of the eternal father.
Here is a nice MP3 of this chant.
