My apologies for the lack of posts in Advent, despatching Ordines has been my priority.
Today is Ember Saturday in Advent and also the Vigil of St. Thomas the Apostle. The rank is simple.
From December 17th a special set of antiphons have been sung at Lauds and the Hours. In the case of today these are the antiphon Intuemini etc. Mattins has one nocturn and three lessons. The second scheme of Lauds is sung (starting with Ps.50, Miserere mei, Deus) and the ferial preces are sung whlst kneeling after the Benedictus. The Vigil is not commemorated in the Office. At the Hours again the special set of antiphons are used in sequence and the ferial preces are sung, kneeling, towards the end of each.
The Mass, sung after None, has the usual, ancient form, for Ember Saturdays. As for all Advent Masses and Ember Days (excepting those of Pentecost) the ministers wear folded chasubles. Four candles are on the altar. After the Kyrie there are a series of structural units comprising of the invitation Oremus, followed by Flectamus genua, Levate, a collect, O.T. reading and gradual. Four of these readings are from Isiah and the last from Daniel. After the pericope from Daniel instead of a gradual the hymn of the Three Men in fiery furnace is sung, Beneditus es, Domine, Deus patrum nostrorum and its collect Deus, qui tribus pueris. After this collect the Vigil is commemorated and the third collect is of the BVM, Deus, qui de Beate. Mass then continues as usual (with of course kneeling for the orations and from the Canon through to the Fraction as usual on penitential days) with Benedicamus Domino as the dismissal and the last Gospel of the Vigil.
A private Mass may be of the Vigil with the second collect of the Ember Saturday, the third collect of the BVM, Deus, qui de Beate. The same praxis about kneeling is followed and Benedicamus Domino sung and the last Gospel of the Ember Saturday.
Vespers of the fourth Sunday in Advent are sung. A series of special antiphons at the Magnificat are used from December 17th (or December 16th in Sarum etc), the great O antiphons. For December 20th this is O clavis David. Exceptionally for a semi-double the O antiphons are 'doubled' and sung entire both before and after the canticle. At compline the preces are sung.
The feast of St. Thomas the Apostle is transferred to Monday.
The unfortunate users of the 'liturgical books of 1962' see the Canticle of Moses at Lauds shortened from 65 to 27 verses. The Vigil of St. Thomas has been abolished. At Prime the ferial chapter Pacem et veritatem.. is replaced by the festal (!) Regi saeculorum.... Ferial preces (that have been sung at all the Hours on feriae) are omitted at Prime and the Hours. The Mass has the option of the 'mini-Ember Day' there is no commemoration of the Vigil or prayer to the BMV, the dismissal is Ite, missa est and the ministers wear dalmatic (the garment of joy!) and tunicle. Vespers, apart from the doubling of the antiphons on the psalms are the same.