The first thing I noticed about this piece happened at about 2:40 of the Introitus, and it seemed to be the theme of "O Come, O come Immanuel." Christmas music being on all our minds at the moment, it was especially apt for me to discover this wonderful piece. I wrote earlier about Dufay, but this piece, of which very little has been written as far as I can find, has captivated me to an even greater degree than previous. Upon first hearing, "The Mass for St. Anthony of Padua", seems to demonstrate more of the massive phrase structures of Ockeghem, which seems to explain why Dufay is considered a predecessor to Ockeghem.
St. Anthony is recognized as the patron saint of Marriage in Portugal, but the wider Catholic Church considers him to be the patron saint of Miracles. His canonization was the quickest of any saint in history, as he was made a saint less than a year after his death in 1231 by Pope Gregory IX.