[quote="porthos11, post:5, topic:307526"]
The same principles apply for Memorials during Advent as in Ordinary Time, but personally, I change my behaviour somewhat, that is, I select other options as provided by the rubrics.
These days, I do the following:
During Ordinary Time, I check the Proper of Saints and see if there is a proper antiphon for the Canticle of Zechariah and Canticle of Mary. If there is, then:
I use the Invitatory Antiphon, Hymn, Reading and Responsory and Intercessions from the Common.
If there isn't, a proper antiphon for the Canticle of Zechariah and Canticle of Mary, I use the Invitatory Antiphon, Hymn, Reading and Responsory, and Intercessions from the Weekday, while I take the antiphons from the Canticle of Zechariah and Canticle of Mary from the Common.
However, during Advent, whatever is not in the Proper of Saints, I take from the Weekday (i.e. Proper of Seasons). I do not use anything from the Common unless the Proper actually directs us to it (a key example is today, December 7, where the Proper for St. Ambrose directs us to use the Hymn from the Common of Doctors. Everything else not from the Proper of Saints, I took from the Weekday and Proper of Seasons.
In Latin, for St. Ambrose, there's actually a proper hymn for Lauds, so that's what I used this morning.
This is one area where there's some latitude. However I am using Les Heures Gregoriennes these days to chant the Office in Latin, and the Propers and Commons are in their own separate volume (and they're HUGE books; there are 3 volumes, Vol I, Advent-Christmas, OT, Vol II, Lent, Easter season, Vol III, saints) so for the sake of convenience, I am using the the Propers when that is required, and the Commons for when there are no propers so I can stick with the same volume.
When I'm using the Monastic Office I have a bit more choices; the volumes are smaller and everything spread among several books in any case. If you pray the Monastic Office, expect to be inconvenienced :( Les Heures Grégoriennes is a brilliantly designed antiphonary, as easy to use as it's possible to do so for the Divine Office.