The Ascension Antiphon on the Magnificat: O Rex Gloriae

While working on my last post, "Vespers for the Feast of the Ascension: Hymnus: Salutis humanae Sator," I noticed something really fascinating.

Listen to this recording of the Ascension Antiphon on the Magnificat, O Rex Gloriae, and see what you notice:



Here's the chant score, from the Liber Usualis:

Does this remind you of anything?   It should.

Now listen to this recording of O Rex Gentium, the Great O Antiphon (that is, the Antiphon on the Magnificat) for December 22 (December 21 in Anglican reckoning):




Here's the chant score for that one:

There's no doubt about it; O Rex Gloriae is a deliberate echo - it even starts with a "Great O"!  - of the Great O Antiphons sung at Advent in the days leading up to Christmas.

Put another way:  the Great O's are sung at Christ's coming;and O Rex Gloriae is sung at Christ's going. 

I truly love discovering this kind of thing....