To me, the Graduale in particular ("Universi, qui te exspectant") is stunningly beautiful - full of gorgeous melismatic musical lines and lovely lilting phrases. Very evocative of the Advent hope and expectant waiting. [Edited to add that I'm now in the process of listening to the others, and the Alleluia, Ostende Nobis is another simply glorious chant for the day; it comes from Psalm 85, I think.] I'm curious as to whether chants like this were ever used in parish settings, or whether they were exclusively monastic. It's amazing how little anybody knows about this anymore, and what a shame that is, because the music is just so beautiful.
Something I find interesting, BTW, is that the text for this chant - and for others for the day - comes from Psalm 25. I checked out the BCP, which doesn't use this Psalm in any of year A, B, or C for Advent 1 - but the RCL does use it, at least this year. But I had understood that the RCL is the "Protestant" lectionary, and that the BCP was normally closer to what the Catholic Church uses. So how come this, then?
One other thing maybe somebody can help me with. Notice that on the website, Psalm 25 is labeled "Psalm 24." I've noticed this before - that the Catholics numbering system is 1 different from ours, but never thought much about it. What's the deal with that? [EDIT: Caelius notes that "The numbering difference is because Psalm 9 and 10 are one psalm in the LXX, but are apparently separate in the Hebrew manuscripts. There's probably a story there, especially since the two psalms form an alphabetic acrostic in Hebrew, just not a perfect one, suggesting a few errors in transmission."]
1 Unto thee, O LORD, do I lift up my soul.
2 O my God, I trust in thee: let me not be ashamed, let not mine enemies triumph over me.
3 Yea, let none that wait on thee be ashamed: let them be ashamed which transgress without cause.
4 Shew me thy ways, O LORD; teach me thy paths.
5 Lead me in thy truth, and teach me: for thou art the God of my salvation; on thee do I wait all the day.
6 Remember, O LORD, thy tender mercies and thy lovingkindnesses; for they have been ever of old.
7 Remember not the sins of my youth, nor my transgressions: according to thy mercy remember thou me for thy goodness' sake, O LORD.