The Great Antiphons of Advent or The O Antiphons of Advent. An antiphon’s purpose is to summarize the main point of the psalm which helps make the connection between the psalm and the service on which it is chanted or sung. These Great Antiphons point the way toward Christmas and Christ. They talk about the Old and New Testaments and summarize the ties that bind everything together. They are a final push and lead us directly to our Lord’s birth, but more importantly, they shed light on the rest of the story and the greater picture.