Today is Ember Saturday in September. The double rite feast of SS Januarius and his companions is the Office of the day. In addition, as the feast of St. Matthew the Apostle falls on Monday, its Vigil is also celebrated today. However, the anticipated Vigil does not get commemorated in the Office because of the Ember Saturday.
This week has been interesting from the perspective of the arrangement of mattins lessons. The feasts of the Holy Cross (Monday) and the Seven Sorrows of the BVM (Tuesday) both had proper lessons in their respective first nocturns. Likewise so did the feast of the Impression of the Stigmata of St. Francis (Thursday) and St. Joseph of Cupertion (Friday). So today, instead of having recourse to the Common the lessons from the Book of Tobias from Tuesday are transferred to today. In the third nocturn the ninth lesson is homily from the commemorated Ember Saturday (its three lessons may be read as one).
At Lauds a commemoration of the Ember Saturday is sung (but not of the Vigil), this has a proper antiphon on the Benedictus and collect.
The Mass, of SS Januarius and his Companions, is sung after Terce. The Gloria is sung, the second collect is of the Ember Saturday (the first collect after the Kyrie and invitation to pray - Omnipotens...), the third collect is of the Vigil, the common preface is sung and the last Gospel that of the Ember Saturday.
Private Masses may be of the Ember Saturday celebrated in violet vestments with the deacon and subdeacon wearing folded chasubles rather than dalmatic and tunicle. The Mass, sung after None, has the usual, ancient form, for Ember Saturdays. 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. The first and second OT readings are from the Book of Leviticus. The third lesson is from Micheas the Prophet, the fourth from the Prophet Zachararias. The fifth is from the Prophet Daniel describing the LORD protecting Azarias and his two companions in the Babylonian fiery furnace. After the reading 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. The feast of SS Januarius is then commemorated with its collect being sung and then the collect of the Vigil of St. Matthew. A Tract is sung between the Epistle and Gospel. 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.
Private Masses may also be of the Vigil celebrated in violet but with the ministers wearing dalmatic and tunicle. The second collect is of SS Januarius and Companions, the third of the Ember Saturday. Benedicamus Domino is sung as the dismissal and the last Gospel is that of the Ember Saturday.
In Cathedral and Collegiate Churches two Masses are celebrated. The Mass of the feast takes place after Terce without any commemorations. The Mass of the Ember Saturday is sung after None with the second collect (before the Epistle) of the Vigil and third collect A cunctis . The dismissal is Benedicamus Domino and the last Gospel that of the Vigil.
When orders are conferred the Tonsure is given after the Kyrie. After the first OT lesson Door-keepers are ordained; after the second, Readers; after the third, the Exorcists; after the fourth, the Acolytes; after the fifth, the Subdeacons; after the Epistle, the Deacons, and before the last verse of the Tract, the priests.
Vespers of the Sunday are sung, the antiphon on the Magnificat is Adonai, Domine of the Saturday before the fourth Sunday of September. A commemoration of the preceding Office of SS Januarius and Companions is sung and then a commemoration of SS Eustace and Companions. The preces are omitted at Compline because of the occurring double feasts.
In the 'liturgical books of 1962' Ember Saturday is postponed by a week and when it does arrive may be celebrated in a typical cut down mini-version. SS Januarius gets cut down to a third class feast of three lessons. Scripture is from last Saturday. The Vigil is not anticipated or celebrated at all as it has been abolished. Vespers has the antiphon that was sung last Saturday in the Old Rite, Ne reminiscaris. No commemorations are made.