The subjection of music TO the liturgy

Protestants are often baffled about why Catholics don't sing all the verses to the hymns. This is usually attributed to Catholics just wanting to "fulfill their Sunday obligation" and get out of there as fast as possible...but I think it is a bit more deeper than that, and even theological.

It is something like this topic that I would someday like to study for something like a doctoral dissertation (ha-if I ever get there. but then again, 2 years ago I NEVER thought I would even be working on my masters...)

But I will try to summarize my (unofficial) thoughts up to this point on this topic:

Catholics have Propers, a prescribed set of texts for every Mass, that can be sung.
but they don't HAVE to be sung.
Mass is perfectly legitimate if the propers are not sung. In fact, if there is no singing at all.
Most Protestants cannot imagine a worship service without singing.
But Catholics come to Mass for more than just to hear a sermon or to sing.
(a sermon is not even essential at a Catholic Mass.)
Catholics come to Mass to witness a Holy Sacrifice, or, at the very least, the high-point of Mass for some of the less-well-informed, but still good-intentioned is, "to receive Communion."
(although, that in itself is certainly not essential to have a Mass-other than for the priest.)
that's why many Catholics walk out the door right after Communion-that's the whole reason they are there.
I am saying all of this to make the point that Catholics come to church for an entirely different REASON than Protestants.
(even, say, Lutherans. While communion is very important for them, I suspect most of the them would be horrified to come to church and neither sing nor hear a sermon.)
Going back to what I said about the propers--they exist FIRST as texts, THEN as melodies (translation issues aside...)
If you've ever witnessed an Extraordinary Form Mass, from the viewpoint of a musician, you would have been struck by how little what the choir is singing has to do with what the priest is doing.
At most places (Gloria, Agnus Dei...) the choir is just singing away while the priest is doing...whatever he's doing. (this exists in the Ordinary Form still with the Agnus Dei, "let's just keep singing verses until the priest is ready with the Host...")
I *think* but I'm not sure, that the Church views this as the ideal--the whole action is never really *supposed* to stop and wait for the music, although it does usually in the Ordinary Form.

And that is what I would like to study more. Read the documents, observe... when-if ever-is the action of the Mass supposed to wait for the singing to be finished?