Absolvimus vos vice beati Petri apostolorum principis, cui collata est a Domino potestas ligandi atque solvendi, et, quantum ad vos pertinet accusatio et ad nos remissio, sit vobis omnipotens Deus vita et salus et omnium peccatorum vestrorum pius indultor. Qui vivit &c.
If a bishop is present, he gives a blessing, and then the Mass begins.
Mass is a little unusual, too. The Officium (introit) is as the Roman use, Nos autem gloriari, but Gloria Patri is only sung if the bishop celebrates. Likewise, there is no Gloria in excelsis unless the bishop is there. The farced Kyrie ‘Conditor’ is mandated for all celebrations, however.
Conditor, Kyrie, omnium, ymas creaturarum, eleyson.
Tu nostra delens crimina, nobis incessanter eleyson.
Ne sinas perire facturam: sed clemens ei eleyson.
Christe, Patris unice, natus de virgine, nobis eleyson.
Mundum perditum qui tuo sanguine salvasti de morte, eleyson.
Ad te nunc clamantum preces exaudias pius, eleyson.
Spiritus alme, tua nos reple gratia, eleyson.
A Patre et Nato qui manus jugiter, nobis eleyson.
Trinitas sancta, trina Unitas, simul adoranda,
Nostrorum scelerum vincula resolve redimens a morte,
Omnes proclamemus nunc voce dulciflua, Deus, eleyson.
The collect is a variant of the Roman one, the Epistle and Gospel are identical. The gradual, too is the same, with the note that if the bishop celebrate, it is either repeated or not repeated (some books have nisi, others ubi!). The Gospel is read ‘in pulpito, more dominicali’ (!) and if the bishop celebrate, then the Gospel is proclaimed ‘more duplicis festi’, and Credo is sung.
The offertorium and secret are the same as at Rome. Meanwhile the subdeacon (or deacon, again a variant) prepares three hosts for consecration. The preface is simply the common daily preface.
There is no separate Chrism Mass, but when he celebrates, the bishop blesses the oils during the Canon of this Mass. At Te igitur, three servers vest in amice and alb, and take up a banner. Three deacons carry the vessels in humeral veils, and a fourth carries a canopy. The archdeacons fill the vessels with oilp.
Before the Per ipsum, the bishop stands aside and the oil of the sick is brought to him, which he blesses.
The oil of catechumens is brought before the blessing (which happens after the Pater Noster, extraordinarily, and is only ever given by a bishop). The bishop then proceeds to the throne.
The Chrism is then solemnly brought in for consecration. First there are three banners, then two acolytes in albs, then two thurifers, then two subdeacons with the book of Epistles and the book of the Gospels, then three singing boys in surplices, then the deacon with the Chrism, the canopy over it.
The three boys in surplices are directed to sing this splendid hymn as they walk before the oil:
Redemptor, sume carnem temet concinentium.
Audi judex mortuorum una spes mortalium.
Audi voces proferentum, dona pacis præmium.
Assit flamen sacrosanctum, olim per diluvium
Qui ramum tulit olivæ ad archam Ecclesiæ.
Arbor fœta alma luce hoc sacrandum protulit,
Fert hoc prona præsens turba Salvatori sæculi,
Consecrare tu dignare, Rex perennis patriæ,
Hoc oleum signum vivum contra jura dæmonum.
Ut novetur sexus omnis unctione chrismatis,
Et medetur sauciata dignitatis gloria.
Stans ad aram, immo supplex, infulatus pontifex
Debitum persolvat omne consecrato consecrato chrismate;
Sit hæc dies festa nobis sæculorum sæculis;
Sit sacrata laude digna nec senescat tempore;
Laus perennis Deo Patri gloriaque Filio,
Honor, virtus ac potestas amborum Paraclito.
The bishop returns to the altar to infuse balsam into the oil and bless the chrism.
Today the Agnus Dei is not said (unless the bishop celebrates when the veneration of the chrism replaces the pax—the chrism is carried to each cleric as a pax brede).
After the communion verse is sung, the office of Vespers immediately begins with the first antiphon. Gloria Patri is not sung at the office. After the Magnificat, the postcommunion prayer is sung. Ite Missa est is only sung if a bishop celebrate, otherwise it is Benedicamus Domino.
Everyone now goes to lunch (and yes, the missal does say that).
After lunch, water is blessed privately. Two senior priests with deacons and subdeacons and candle bearers all vested in amices and albs go to the high altar and wash it with wine and water while the responsory In monte Oliveti is sung, without Gloria Patri. Then the antiphon and collect of the saint in whose honour the altar is consecrated is read, and the same process is carried out for all the altars in the church. There are a lot of responsories provided for singing meanwhile.
Then everyone goes to the chapter house for the Mandatum.
The Gospel from the Mass is read again, and a sermon is preached. The same priests who washed the altars rise and each wash the feet of all the clergy from one side of the choir, and then each other’s. There are lots more antiphons and responsories to sing meanwhile. Then all share a ‘loving-cup’, while Christ’s farewell discourse is read, (John 13:16—14:31) and the celebration concludes with some prayers and then all return to the church where they recite the office of Compline privately.
As to what happened to the Blessed Sacrament, whether it was placed in an altar of repose, or in the sepulchre, or simply returned to its usual place of reservation, the books I have are silent.
After I wrote this post, I discovered a reference to the third Host being brought from the 'Altare Authentica' to bury in the sepulchre on Good Friday. This altare authentica is probably to be identified with the high altar, and therefore we assume that there is no altar of repose, but that the Blessed Sacrament is simply reserved at, or over, the high altar as usual. The ceremonies that we associate with the altar of repose are observed the following night, then, at the sepulchre.