I would say no to that one. The TLM gradually developed over the course of the first millennium and has been enriched over a considerable period of time. Indeed the Missal of Pius V (1570 ) was very similar to the first known printed edition from 1474 which itself would have been recognisable to Pope St. Gregory the Great in the 6th Century
If we’re talking about the basic structure (i.e. the text) this indeed would be the case. We need not oversimplify things though since the rubrics, the vestments and
the chant used would have been naturally different. Here are some of them:
- The Offertory was, as per the name, the time when the people offered their gifts and when the clergy prepared the altar. There were no prayers during the Offertory then, except for the Secret.
- There was no Creed, its recital being introduced only into Rome at the behest of Henry II in 1014. That being said there were no Prayers at the Foot of the Altar or Confiteor either.
- The length of some chant was not fixed (for example the Introit and the Kyrie); the choir would usually continue singing the Psalms until given a signal by the Pope to finish.
- There was no elevation of the Sacred Species during the Words of Institution yet (this being introduced only at the close of the 12th century and later); the only elevation of the Body and the Blood there was is when the archdeacon lifts the chalice, carrying it using the offertory-veil twisted in the chalice’s handles, with the Pope touching its sides using the consecrated loaves at the Per ipsum.
- There were the two customs of the Sancta and the Fermentum. The Sancta refers to the custom of putting into the chalice at the Pax Domini a fragment consecrated at the preceding Mass and brought forth at the beginning of the present one (two acolytes usually come carrying fragments of the Eucharist consecrated during the Introit for the Pope to check). The Fermentum, meanwhile, refers to the custom of sending consecrated bread from the bishop’s (Pope’s) Mass to the priests whose duty it was to celebrate in the titular churches of Rome. Thus, in all the churches of Rome, and at every assembly there for liturgical worship past or present, there was always the same Sacrifice, the same Eucharist, the same Communion.
- The way some of the clergy (aside from the Pope, who receives from his cathedra) communicate is quite curious. They receive the Bread from the hands of the Pope, go to the end of the altar - bishops and priests to the left, with the deacons to the right - and then consume the Eucharist there. The other clergy were later communicated by the Pope and the bishops (Body), and the archdeacon and the other deacons (Blood).
- Lay communicants usually received the Precious Blood through a type of straw (a custom which was preserved in Papal Masses of later ages). The Precious Blood consumed by laymen was hallowed indirectly by addition of a small quantity of the one consecrated by the Pope.
- Communion was also the time when the next Station was announced and when the Pope - through the notaries - handed out invitations for breakfast with him or his vicar to certain people.
- Overall, there was more bowing and less genuflecting.
- Incense was also less used (the more frequent use of incense in later days was due to the influence of the Gallican Rites): it was employed only when the Pope arrives at the stational church, when he makes his way to the altar at the beginning of the Mass, and when the deacon goes up to the ambo. Some basilicas might have a hanging censer before an icon or an altar, burning throughout the liturgy.
- Mass back then took a long time to finish, especially if there was a sermon and if there were a large number of communicants. Pope St. Gregory the Great in fact once complained to the Patriarch Eulogius of Alexandria how he was afflicted with such severe gout that he scarcely had the strength to stand to offer the Liturgy on solemn feastdays, which lasted three hours (!).
The above is mostly based on the First
Ordo Romanus. Thus the Catholic Encylopedia tells us:
The first of these Ordines Romani, describing the ceremonies of a solemn Mass celebrated by the pope himself or his deputy, is the most valuable, as it is also one of the most ancient. Modern opinion inclines to the belief that the early part of it (numbers 1-21) really represents in substance the usages of a stational Mass in the time of Pope Gregory the Great (Kösters, “Studien zu Mabillons röm. Ord.”, 6; cf. Grisar, “Analecta Romana”, I, 193), but there are also, undoubtedly, in our present text adjustments and additions which must be attributed to the end of the seventh century (Atchley, “Ord. Rom. Primus”, 7, favours a later date, but in this he only follows Probst). The fact that Amalarius, who seems to have had a copy of this Ordo before him did not find its description of paschal ceremonies in agreement with the actual Roman practice of his day, as expounded to him by Archdeacon Theodore in 832, need not lead us, with Mönchemeyer (“Amalar”, 141), to the conclusion that the ceremonial never represented the official Roman use, and that it was merely an outline serving as a model for similar ceremonies in the Frankish dominions. On the contrary, so far as regards numbers 1- 21, every detail attaches itself in the closest way to the pontifical ceremonies of Rome.
They were not laity at that point.
