From a priest reader:
In my Wilfrid Diamond dictionary of liturgical latin, the entry for “epiclesis”, is f., says, “an invocation. The “Supra quae” in the Mass. In the Greek Church a calling down of the Holy Spirit.”
Is the Supra quae an epiclesis (Upon which…)?; it seems to be addressed to the Godhead and not the Holy Spirit, per se.
However, I noticed right away that the “Veni, Sanctificator” just before the Washing of the Hands clearly addresses the Holy Spirit–could this be the epiclesis in the Low Mass. I understand this may be a common question, so forgive me.
My understanding is that, while there is no explicit epiclesis before the consecration, the Roman Canon has texts which are understood as such.
In the Extraordinary Form there was the Veni sanctificator prayer, of course. This together with the Quam oblationem sufficiently express the intention. After the consecration there is the Supplices te rogamus. So, before the Canon begins and at the Canon’s end there are explicit invocations of the Holy Spirit.
So, the Quam oblationem is the main focus in your question. The new translation renders it this way:
Be pleased, O God, we pray, to bless, acknowledge, and approve this offering in every respect;make it spiritual and acceptable,so that it may become for us the Body and Blood of your most beloved Son, our Lord Jesus Christ.
You can understand the thought behind moving the priest’s palms-down gesture over the bread and wine, from the Hanc igitur to the Quam oblationem in the Novus Ordo. In the Extraordinary Form, that gesture (during the Hanc igitur) seems to be more a gesture denoting a transference. It seems to be closer to the gesture of the ancient Jewish priests over the scapegoat, as described in Leviticus 16. Moving it to the Quam oblationem makes it seem to be more of a calling-down gesture.