From Fr. Hunwicke, something provocative… with my emphases and comments:
“Pray Brethren that my sacrifice and yours …”
We find the roots of this formula, which precedes the Prayer Over The Offerings, in Carolingian Gaul, in a rubric which goes: “Then indeed the Priest to [or with?] right hand and left asks of the other priests that they pray for him”. [In case someone from Columbia Heights missed that… “the other priests” and not the congregation!]
I am suggesting that originally the Orate Fratres was a formula addressed to concelebrants; although, of course, through being used by celebrants who had no concelebrants around them, it soon came to be thought of as addressed to the assistant clergy in the sanctuary and to the congregation.
The strength of my suggestion is that it makes sense of the concept of “my sacrifice and yours”. I have long been puzzled by the assumption we have all made that a formula which entered the Mass as late as the Carolingian period should seem to want so explicitly to refer to the People as offerers of the Sacrifice. Yes, I know that in a sense they most certainly are, [By baptism they have a priestly character at Mass, but not in the same way the priest is priestly.] but that was a period in which emphasis was laid more and more strongly on the idea that the Priest sacrifices for the people (so that the phrase “for whom we offer unto thee” entered the Memento).
Surely the eventually diminishing of concelebrants and priests in choir for most Masses permitted a shift in meaning. However, in recent years there have also been relentless efforts to pull the priest down and to diminish him.