Since Easter is a moveable feast, and Christmas is not, something sort of strange happens at the end of the Liturgical Year. Differently strange in the Ordinary and Extraordinary Forms, but strange nonetheless.
In the Ordinary Form (that is, the mass most are familiar with, in the vernacular), the last Sunday before Advent is the Feast of Christ the King. The Sunday before is always the 33rd Sunday in Ordinary Time, even if it actually isn’t. The Ordinary Form has readings for 33 Sundays, but, if, for example, Easter falls late, you’re going to have to miss a few somewhere in there. To make it work out, the Ordinary Form Calendar starts with the 2nd Sunday on the Sunday after Epiphany (because most places transfer Epiphany to Sunday, and Epiphany trumps a regular Sunday in the hierarchy of liturgical celebrations), and goes forward until Lent (which can move). Then, to figure out when to pick back up, the calendar counts backwards from the 33rd Sunday, and stops when it hits Pentecost. This means the “missing” readings come from the 3-4-5th or so Sunday of Ordinary Time.
In the Extraordinary Form, the chanted propers (that is, the Introit, Gradual, Offertory, and Communion) stay the same from the 23rd Sunday after Pentecost until the First Sunday fo Advent. However, there are always more than 23 Sundays after Pentecost (I think at least 25), so the propers get put on repeat. The readings are a different story: they get borrowed from the Sundays after Epiphany. Corpus Christi Watershed has a great post from 2015 explaining this.
The upshot is that the Schola Cantorum (that is, those doing the chanting) have the opportunity to get really good at these propers. That’s not to say that you can stop paying attention, but you do get multiple chances to perfect De profundis. This year, we get four Sundays with the same propers, so four chances to really nail it.
Now you know why it sounds like your Schola Cantorum is stuck on repeat.