The fourth Sunday of Advent this year is the Vigil of the Nativity of the LORD. The Vigil of the Nativity changes its rank from simple to double after Mattins.
At Vespers yesterday afternoon the antiphons and psalms of Saturday were sung. The chapter, Fratres: Sic nos existimet homo was from the first Epistle to the Corinthians, the Office hymn was Conditor alme siderum. The antiphon on the Magnificat was O Emmanuel which was sung entire both before and after the Canticle with the choir standing. After the collect of the Sunday the usual Suffrages are omitted during Advent. At Compline the Dominical preces were sung.
At Mattins the invitatory is Hodie scietis quia veniet Dominus, Ex mane videbitis gloriam ejus, from the Vigil, and the hymn is Verbum supernum prodiens. In the first nocturn (of the Sunday) the antiphons Veniet ecce Rex etc are sung with Pss. 1, 2, 3, 6, 7, 8, 9, 10, 11, 12, 13 & 14. The lessons in the first nocturn are taken from the prophet Isaiah. The first and second lessons are the same as those found in modern editions of the Breviary. The third lesson is slightly longer continuing Viderunt insulae ... eum clavis, ut non moveretur, (i.e. the addition of Cap. 41 vv. 5 -7). In the second nocturn the antiphons Gaude et laetare etc are sung with Pss. 15, 16 and 17. The lessons are taken from a sermon of St. Leo on fasting in the tenth month. These are substantially longer than in the modern editions of the Breviary. The sixth lesson text is completely absent from the modern editions. In the third nocturn the antiphons Gabriel Angelus etc are sung with Pss. 18, 19 and 20. After the last antiphon a versicle proper to the day, Hodie scietis, quia veniet Dominus, and its respond, Et mane videbitis gloriam ejus. The homily (of the Vigil) is taken from St. Jerome's commentary on the first chapter of St. Matthew's Gospel. The seventh lesson consists of the text of both the first and second lessons (of the Vigil) in the post-Clementine books. The eighth lesson is the same as the modern third lesson (of the Vigil). The ninth lesson, Joseph fili David noli timere (...) salvum faciet populum suum, is entirely absent from the post-Clementine books. A ninth responsory, Sanctificamini, is sung in place of the Te Deum. At Lauds the antiphons, Judaea et Jerusalem nolite timere etc (sung under double rite), are proper to the day and are sung with the psalms of Sunday (92, 99, 62-66, Benedicite and 148-149-150. The Office hymn is Vox clara ecce intonat. The V & R, chapter, antiphon on the Benedictus, and collect are proper to the Vigil. The ferial preces are not sung.
Prime is festal with the first antiphon from Lauds, as usual, and psalms 53, 118(i) and 118(ii). The Martyrology is sung with extra solemnity today. The Hebdomadarius dons a violet cope and preceded by acolytes bearing candles and a thurifer with incense enters the choir. After reverencing the choir and altar the Martyrology is censed, as a Gospel book, three times. The the choir rise and the Hebdomadarius chants 'Octavo Kalendas Januarii. Then, after announcing the moon, continues Anno a creatione mundi, quando in principio Deus creavit coelum et terram, quinquies millesimo centesimo nonagesimonono: A diluvio etc., listing the years since the birth of Abraham, the Exodus from Egypt, the anointing of David, the time since Daniel the Prophet, since the founding of Rome and the conception of the LORD by the Holy Ghost '...novemque post conceptionem decursis mensibus', then raising the pitch of the chant, whilst the choir kneel, he continues, 'in Bethlehem Judae nascitur ex Maria Virgine factus Homo'. Then in the tone of the Passion: 'Nativitas Domini nostri Jesu Christi secundem carnem.' The choir then rise and sit whilst in the normal tone the Hebdomadarius (or a lector, depending on the custom of the place) continues with the entries for the day: 'Eodem die natalis santae Anastasiae etc. The lectio brevis, Per quem accepimus, is proper to the Vigil. The antiphons from Lauds are used in sequence at the rest of the Hours.
Mass is sung after None. Today the ministers do not wear folded chasubles but dalmatic and tunicle. There is just one collect. The dismissal, Benedicamus Domino, is sung by the deacon to a most beautiful and ornate tone reserved for today, the feast of the Holy Innocents and pro re gravi Masses.
First Vespers of the Nativity are sung in the afternoon. The antiphons Rex pacificus etc are sung with psalms 109, 110, 111, 112 & 116. All hymns of Iambic metre have the Doxology Gloria tibi Domine, Qui natus es de Virgine for the Octave and up until the feast of the Epiphany.