Usually, insofar as possible, the Masses held each year at the sacred music colloquium sponsored by the CMAA are said ad orientem; only a few have been said versus populum. In 2006, the annual Requiem Mass (new rite) was held in the chapel in Caldwell Hall on the campus of Catholic University of America. The altar in use there is freestanding, and the celebrating priest offered the Mass versus populum.
But then an interesting thing happened. When Father started the Eucharistic prayer, his voice got very soft, even though, if I recall correctly, he was chanting. It truly was a remarkable moment. I spoke to the priest about this at lunch afterwards, about how much this approach emphasizes the theocentric character of the liturgy.
He leaned over and said to me very intently, "The Almighty, the maker of all ears, has excellent hearing."
That pretty much sums it up.
I noticed recently that another priest here in Philadelphia whom I know does the same thing. I commented to a friend about this, who said something quite insightful: This may be the way to transition people from versus populum celebrations of the Mass to ad orientem celebrations. That's not a bad idea.
Besides emphasizing the theocentric nature of the liturgy, the softer pronunciation of the Canon or other Eucharistic prayer highlights the most sacred character of this part of the liturgy. Sacred objects are usually veiled; this tradition goes back to Judaism. Similarly, the Canon can be at least partially veiled by a medium volume voice, as opposed to the high volume voice to which most are now accustomed. (The best option, in my opinion, is the silent Canon, but since we're talking about intermediate steps, that is not germane to this post.) I can attest from personal experience that when the priest does this, the atmosphere of the liturgy changes drastically for the better.
Another thought not entirely unrelated to the above has struck me with respect to the music employed at the innovative Memorial Acclamation. Most times, after the priest or deacon has said, "Mysterium fidei," the organist pulls out the loud stops, then cues the timpani entrance, followed by the soprano descant and the trumpet flourish. But is this kind of musical rendition in keeping with the part of the liturgy which it serves? It seems to me that at this part of the Mass, a quieter approach is fitting. Save the trumpets for the Amen. I have begun to follow this rule at the Novus Ordo Masses at which I play, and it really seems to come off as much less of a rude interruption of the Canon. Organists may wish to consider this idea.