This 3rd O Antiphon is "O Radix Jesse." The root, or stock of Jesse. It highlights the messianic element of Christ in his lineage in King David - Jesse being David's father. Thus we have a chant to Christ our Ruler, and Messiah.
The "O" is once again emphasized, and this time with the element of the trinity specifically considered. In worshiping Christ, Who is God incarnate (the son of David) the whole of the Trinity is considered in this "O."
The first note begins on the root of the chord, which is the foundational note the chord is built from, and this represents the Father. The second part of the "O" moves to another chord for the Son, and the note sung is the root note of the chord but the 3rd, and this represents Christ the man Who by His incarnation brought harmony between man and God. The third part of the "O" drops in a sequence of notes and does not fall on one chord, and so speaks of the Spirit, Who does not speak for Himself but speaks of the Father and the Son, The descending order of these last notes also represent the Spirit "falling upon us."
Like before this is the recording as I sent it to the musicians at The Gathering.
This is part of an Advent Synchroblog. For the other posts which are a part of this series see the Synchroblog Wordpress Blog.