The O Antiphons

An article by Fr. William Saunders tells us:

The “O Antiphons” refer to the seven antiphons that are recited (or chanted) preceding the Magnificat during Vespers (Evening Prayer) of the Liturgy of the Hours. They cover the special period of Advent preparation known as the Octave before Christmas, Dec. 17-23.

…The importance of “O Antiphons” is twofold: Each one highlights a title for the Messiah: O Sapientia (O Wisdom), O Adonai (O Lord), O Radix Jesse (O Root of Jesse), O Clavis David (O Key of David), O Oriens (O Rising Sun), O Rex Gentium (O King of the Nations), and O Emmanuel. Also, each one refers to the prophecy of Isaiah of the coming of the Messiah. Let’s now look at each antiphon with just a sample of Isaiah’s related prophecies.

The O Antiphons are reflected in the hymn commonly sung throughout Advent: “Veni, Veni  Emmanuel”.

In another article on the New Liturgical Movement blog,  Gregory DiPippo gives the following introduction to the O Antiphons. It’s an interesting article, well worth reading in its entirety.

We are now in the final days of Advent, in which the famous "O" Antiphons are sung each day at Vespers with the Magnificat. These are one of the most loved features of the Church's liturgy, and for good reason; the texts are especially rich in references to the Old Testament prophecies of the Divine Redeemer and His coming for the salvation of the human race, and the Gregorian chant with which they are sung is extremely beautiful. The Roman Rite has seven of these, and it of course well known that the first letters of the seven titles (O Sapientia, O Adonai etc.) form an acrostic when read backwards, ERO CRAS, Latin for "Tomorrow I will be."; this is completed on the last day before the Christmas season formally begins on the evening of the 24th.

Fr. Z also has comments on the O Antiphons, updating them daily as the O antiphon changes, and mentioning the corresponding verse of “Veni, Veni Emmanuel”. Today’s entry:

LATIN: O Radix Jesse, qui stas in signum populorum, super quem continebunt reges os suum, quem gentes deprecabuntur: veni ad liberandum nos, iam noli tardare.
ENGLISH: O Root of Jesse, that stands for an ensign of the people, before whom the kings keep silence and unto whom the Gentiles shall make supplication: come, to deliver us, and tarry not.

Relevant verse of Veni, Veni Emmanuel:O come, O Rod of Jesse free,
Thine own from Satan’s tyranny;
From depths of hell Thy people save,
And give them victory o’er the grave.

Fr. Z also makes some interesting theological points developments concerning the prayers for the Masses of these last days of Advent:

The prayers for the final days of Advent, therefore, in the Ordinary Form are intended to bring the participation to a deeper contemplation of the mystery rather than the deeper pursuit of penance before the feast day.  Keep in mind that the celebration of Christmas at Rome and in the West in general, developed rather late.  Also, in the mid-5th century, in 431, the Council of Ephesus dogmatically identified Mary as “Mother of God”.  These are certainly influences at work behind the prayers of the Rotulus. There inclusion in the formulae of Masses in the last days of Advent in the Ordinary Form create a dramatic change in our theological direction in comparison with the Masses before Christmas in the Extraordinary Form.