Here is the Processional Music for the Third Sunday in Advent. The Antiphon prior to the station is "O Come ye" and the Responsory after the station is "Behold the Rood". The antiphon for the 4th Sunday, which is coming up, is the same, but the Responsory will be different.
For commentary on things Western Orthodox, including the chant music, and mass propers, processional music, etc, etc go to our other blog.
Especially on the Western Orthodox services page you'll see a number of scanned material already; including some propers and processional music.