For a couple years I’ve posted about this custom. This year I had pretty much forgotten about it until I got an email from a priest who asked for a recording of this year’s version. The main text does really change but the intro does. It all has to do with the Moon. It’s complicated.
It was a custom for centuries to sing the Kalendas, the solemn announcement of the birth of the Savior at Prime. Since Prime isn’t being sung in many places, and since we need to have these good customs in far greater use, I say go ahead and sing it before Midnight Mass in the Vetus Ordo. Heck, the Novus Ordo too. Why not?
In the proclamation, the birth of Christ follows a list of important events, set points in history, which therefore puts the birth of Christ into the context of the history of salvation, beginning with the Creation of the world and culminating in the Nativity.
Remember that in the ancient world there was no standard calendar. So, one way to pinpoint events was to say what else was going on at the time according to other reckonings of time. The overlap of the dates would then give you the desired result, like a chronological Venn Diagram. The overlapping of the dates of the events cited in the Proclamation results in an accurate dating of the Nativity, that is 3/2 BC. There is good scholarship that reinforces 3/2 BC and cleans up a dating error for the year of Herod’s death.
The older Roman Martyrology has the notation for the Modus Ordinarius. It is rather like the “prophecy tone” and you raise the pitch at certain places.
There is a fancier rendering which is provided by Cappella Gregoriana Sanctæ Cæciliæ olim Xicatunensis. HERE
Here’s what the Kalendas sounds like more or less, if you can stand my singing without much of a review. I also find it interesting that as I started this there was one noisy interruption after another.
And keep in mind there is also on Epiphany the singing of the announcement of the moveable feasts for 2023, the Noveritis, “Let y’all know”, which does change quite a bit from year to year for obvious reasons.