Fire away with your questions, I'll do my best to answer!
Remember: you asked for it.
The Collect for Purity [Tikhon] - This prayer dates to at least the 8th century, and is unique to the English liturgical heritage.
What is the text of this prayer, and what liturgy does it come from if it is so old but only appears in the "English" rite and not the "Roman"?
"Almighty God, unto whom all hearts are open, all desires known, and from whom no secrets are hid; cleanse the thoughts of our hearts by the inspiration of Thy Holy Spirit, that we may perfectly love thee, and worthily magnify Thy Holy Name; through Christ our Lord. Amen."
This prayer can be found in the Sacramentary of Alcuin (d. 804) as well as the Sarum Mass, as seen in the 11th c. Leofric Missal.
Preparatory Prayers [Gregory & Tikhon] - These two prayers are prayed by the Priest only. One dates from the 6th century, the other from the 11th.
What prayers are these that occur in both rites? Aufer a nobis and Oramus te Domine?
You are correct. In English, they read as follows: "Take away from us, we beseech Thee O Lord, all our iniquities that we may enter the Holy of Holies with pure minds. Through Christ our Lord Amen." The priest then kisses the altar and says, "We beseech Thee O Lord, by the prayers of (Thy Saints whose relics are here, and of) all Thy Saints, that Thou wouldest vouchsafe to forgive all my sins. Amen."
The Summary of the Law [Gregory & Tikhon] - Here is given the summation of the Old Covenant by Our Lord Himself, as found in St. Matthew 22:37-40 and St. Luke 10:25-28.
I presume this is one of those "English enrichments" of the Roman Mass? What is its text and function?
This is actually unique to the Tikhonian liturgy, I accidentally put Gregorian here. The texts are, "Hear what our Lord Jesus Christ saith: Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. This is the first and great commandment. And the second is like unto it, thou shalt love thy neighbor as thyself. On these two commandments hang all the Law and the Prophets."
This is still connected to all of these other prayers of preparation; the Asperges, Prayers at the Foot of the Altar, Collect for Purity. It is "acclimating" us, to so speak, to the Holy Mystery we are about to enter into. We are presented with Christ's authoritative summary of the entirety of God's revelation in the Old Covenant, which Christ boils down for us as the very essence of Christian life, because we cannot partake of His Body and Blood unless we have our priorities in order ("But let a man examine himself, and so let him eat of that Bread, and drink of that Cup" 1 Cor. 11:28).
Kyrie Eleison [Gregory & Tikhon] - The first instance of the Kyrie being described in the worship of the Western Church comes to us from a council held at Caisson in 529 AD, the third canon of which states that, “since both in the Apostolic See, and throughout all the provinces of the East of Italy, the sweet and extremely salutary custom has been introduced of saying ‘Kyrie eleison’ with great feeling and compunction; it pleases us, too, that in all our churches this same holy practice shall be introduced both at Matins, Mass and Evensong.”
Gloria in Excelsis [Gregory & Tikhon] - The Gloria was introduced in Rome in the 5th century, in imitation of the Church of Jerusalem. It was originally a Greek hymn, forming part of their morning services, and was finally set in the Western Mass, as we read in the Life of St. Symmachus (498-514 AD), where he appointed the angelic hymn to be sung every Sunday or festival of a martyr. The present text as we have it now was translated into Latin by St. Hilary of Poitiers (300-368 AD).
I haven't consulted Jungmann on this question, but I've noticed that both Armenian and Syriac Liturgies begin the Liturgy of the Catechumens with what I suppose is a primitive form of the end of Matins and/or the Third and Sixth Hours. My sense is that something similar is going on with Byzantine and perhaps Coptic Liturgy. In all cases, the Matins/Hours developed on their own but seem to have retained these elements, and in at least some cases, they are part of those services even when the Liturgy is not served. Is it possible that the Kyrie and Gloria are functioning in a similar way in the Roman Mass, as a sort of transition from a primitive morning office to the Liturgy proper?
It's possible, but my understanding is that it is actually replacing a litany. St. Gregory the Great said, "We neither said nor say Kyrie Eleison as it is said by the Greeks. Among the Greeks all say it together, with us it is said by the clerks and answered by the people
, and we say Christe Eleison as many times, which is not the case with the Greeks. Moreover in daily Masses some things usually said are left out by us
; we say on Kyrie Eleison and Christe Eleison, that we may dwell longer on these words of prayer" (Ep. ix in P.L., LXXVII, 956)
The Gloria, on the other hand, seems to have grown out of the Mass for Christmas, added to each Sunday only later, in the 5th century, and only to be said by bishops.
Prayer for the Whole State of Christ's Church [Tikhon] - Here the Tikhonian liturgy departs from the Gregorian and follows more closely to the East. This prayer is rooted in St. Paul the Apostle's directive to "make intercessions for all men" (1 Timothy 2:1) and is directly parallel to the Great Litany of the Divine Liturgy of St. John Chrysostom.
IIRC, such a "universal prayer" was located at the Dominus vobiscum before the offertory verse: is there a reason why your rite has placed it after and not before the offertory? And what form does it take?
The form is,
"ALMIGHTY and everliving God, who by thy holy Apostle hast taught us to make prayers, and supplications, and to give thanks for all men; We humbly beseech thee most mercifully to accept our [alms and] oblations, and to receive these our prayers, which we offer unto thy Divine Majesty; beseeching thee to inspire continually the Universal Church with the spirit of truth, unity, and concord: And grant that all those who do confess thy holy Name may agree in the truth of thy holy Word, and live in unity and godly love.
We beseech thee also, so to direct and dispose the hearts of all Christian Rulers, that they may truly and impartially administer justice, to the punishment of wickedness and vice, and to the maintenance of thy true religion, and virtue.
Give grace, O heavenly Father, to all Bishops and other Ministers [remembering N.N.], that they may, both by their life and doctrine, set forth thy true and lively Word, and rightly and duly administer thy holy Sacraments.
And to all thy People give thy heavenly grace; and especially to this congregation here present; that, with meek heart and due reverence, they may hear, and receive thy holy Word; truly serving thee in holiness and righteousness all the days of their life.
And we most humbly beseech thee, of thy goodness, O Lord, to comfort and succour all those who, in this transitory life, are in trouble, sorrow, need, sickness, or any other adversity.
And we also bless thy holy Name for all thy servants departed this life in thy faith and fear; beseeching thee to grant them continual growth in thy love and service, and to give us grace so to follow their good examples, that with blessed Mary and all thy Saints, we with them we may be partakers of thy heavenly kingdom. Grant this, O Father, for Jesus Christ’s sake, our only Mediator and Advocate. Amen."
The prayer is placed where it is because it is connected to both
the offertory and the Eucharist. It is understood to be the conclusion of the Offertory and the first stage of the Eucharist. It was placed here when it was discovered that this was the ancient position for it, as described by St. Justin Martyr. It used be after the Sanctus.
General Confession [Tikhon] - Also unique to the Tikhonian liturgy is this prayer of confession followed by absolution. This follows more closely (than either the Roman Mass or the Byzantine liturgy) the more primitive forms of the liturgy which contained an absolution for penitents.
I like it.
The Comfortable Words [Tikhon] - These are short sentences of Scripture, specifically quotations from Our Lord, St. Paul the Apostle, and St. John the Divine.
What is the function of this element?
Through these passages the faithful are assured of the confidence we have in forgiveness so that we can "draw near with faith" (perhaps corresponding to the East's "holy things for the holy"?).
It is rooted in this verse, as well, Hebrews 10:22 (KJV): “Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water.”
It should be noted that here, "comfortable" doesn't carry with it the modern connotation of, say, "a comfortable chair" but in the sense of the Holy Spirit is the "Comforter."
The Lord's Prayer [Gregory & Tikhon] - In a letter of St. Gregory’s, from 598 AD, we read regarding the placement of the Lord’s Prayer, “But we say the Lord’s Prayer directly after the canon for the following reason: because it was the custom of the Apostles to consecrate the sacrificial oblation solely with this prayer. And it seemed to me extremely unsuitable to say over the oblations the canon, which was composed by some learned man, and not to say over his Body and Blood that prayer which our Redeemer himself composed.”
Thank you for this, I'd never heard it before. Do you know of a source for this?
The source is a letter of Pope St. Gregory to John, Bishop of Syracuse, dated 598 ad (Epistle xii).
The Thanksgiving [Tikhon] - This is yet another instance where the Tikhon tradition follows the more primitive model, whereas the Gregorian Mass gradually lost its prayers of thanksgiving directly following Holy Communion. This prayer corresponds to one found in the Liturgy of St. James.
Postcommunion Collect [Gregory & Tikhon] - This element is found in the oldest of Western Sacramentaries, the Gelasian.
I thought the Collect was the Thanksgiving...the Roman Mass used to have a separate prayer of thanksgiving?
I should have said, rather, that they became private
prayers of the priest, not that they disappeared altogether. The Tikhon Rite is restoring the practice of this being a public Thanksgiving. But, yes, the Collect serves for this as well. You can't give too much thanks, can you?
The Blessing [Gregory & Tikhon] - This became fixed by the 11th century. There is another difference between the two liturgies here, the Tikhonian form being longer and derived from an old Anglo-Saxon episcopal blessing, found in the Exeter Pontifical (11th c.).
Do you have the text for the Tikhonian form?
It's a subtle difference, but the Tikhon form is:
Deacon: The Lord be with you
People: And with thy spirit
Deacon: Depart in peace
People: Thanks be to God
Priest: The Peace of God, which passeth all understanding, keep your hearts and minds in the knowledge and love of God, and of His Son Jesus Christ our Lord; and the Blessing of God Almighty, the Father, the Son, and the Holy Ghost, be amongst you and remain with you always. Amen.
The Gregorian is the same, but the Priest's blessing is: May Almighty God, the Father, the Son, and the Holy Ghost, bless you. Amen.
The Last Gospel [Gregory & Tikhon] - This second Gospel reading emerged from the private devotions of the Priest and is usually the Prologue from the Gospel of St. John the Divine.
I don't know why, but I really like this practice. I regret that in most Latin Mass communities I've visited, the priest mutters this to himself rather than read it aloud: if it's a private devotion, do it in the sacristy, but if you're going to read the Gospel at the altar, then proclaim it from the altar.
Indeed, we treat it the same as the Gospel reading in the Mass of the Catechumens. We stand, cross our forehead, lips, and heart and listen to this most profound of readings. Mass would not be the same without it.
That's all for now.
Hope this was helpful. I'm no expert, just have an avid interest.