Good question. The simple answer back in 1903 was chant, whether Latin plainsong or other cultural forms from various geographical customs such as Sarum chant, Ambrosian chant, Syriac chant, etc. And there are many proponents that this solution remains the last, best hope for a liturgical salvation. Google "Regina Magazine Online" and look for a recently published article "How Catholics Got their Chant Back" (or something like that title.)
In this era, presuming that the vernacular Ordinary Form is here to stay, I would offer that "universal" presages that sacred music for worship must maintain some readily identifiable "Roman Catholic" ethos. So, the new chant settings in English, the new Mass Ordinaries, service music and motets that employ the classic features of sacred polyphony of the Renaissance "golden era" and even Eastern Orthodox homophony in the vernacular meets that criterium.
As our CMAA president Wm. Mahrt oft says, "Does this music sound like it BELONGS in church?"
And I often imitate another starting point as Mahrt, "If you hear the celebrant priest chanting his orations instead of reciting them, you know you're in a catholic church.

Close, Chris, Scots.

Was that the late Ian McCallum's character, Chris?
Y'know how James Taylor sings "Goin' to Carolina in my mind?"
I substitute "Braemar" there, even tho' I have NC Scots landed here in 1612.
I left a beret in their parish just so's I could have a reason to gae back.

Yes carpeting is awful. Our pastor replaced the carpet in the sanctuary of our very modern church with tile. The sanctuary is about a 1/3 of the church. The difference was marked, I think in part to the fact that there are few people in the sanctuary and clothing does not affect the resonance there.

At the colloquium David Hughes mentioned that a church's (perhaps his church?) ceiling was repainted using enamel (I believe!) paint and the resonance improved dramatically! What a difference this would make in our huge church with (no joke) a popcorn covered ceiling!

We are putting acoustic tiles on the ceiling of our new church to reduce overtones. I have raised objections but in the end we've decided to trust the sound engineer to the amount of treatment required without damaging the acoustics of the space. We only have two microphones mounted to the ceiling above the choir loft for a little extra sound re-enforcement.
We'll see how it all comes together after its built.

I can't at this point because the church is just being built. We've hired an acoustician and sound engineer, who have convinced the rest of the building committee, the architect and pastor that we need some acoustic tiles to reduce overtones and that the natural delay and reverberation will be maintained.
I have tried to convince them that it is probably not necessary but they are trusting the hired experts in sound design.
I talk with the sound engineer on the phone and have informed him that we will be singing chant, polyphony and will have an organ. And he says that we will not need amplification.

Donr,

How much of the money you are going to pay to the acoustician might otherwise be available for the purchase/building of a pipe organ?

If you're building a brand-new church, you don't need acoustical tile to resolve a problem which doesn't exist yet.

I can't at this point because the church is just being built. We've hired an acoustician and sound engineer, who have convinced the rest of the building committee, the architect and pastor that we need some acoustic tiles to reduce overtones and that the natural delay and reverberation will be maintained.
I have tried to convince them that it is probably not necessary but they are trusting the hired experts in sound design.
I talk with the sound engineer on the phone and have informed him that we will be singing chant, polyphony and will have an organ. And he says that we will not need amplification.

Have them all agree to not do anything until you are in the church.

Otherwise you are, to use the technical term, screwed.

Recently designed an organ for a major university. President, in meeting, told them to NOT to anything to the cruciform building until they were in it. Period.

Got in there and the arms of the cross had acoustical material on the facing walls.

Sucks up all the sound from the organ and choirs, piano and all, leaving a very strange echo from the back wall from what little sound makes it through that area.

Dean of Music, a choral director, is aghast.

Acousticians and sound engineers are engineers. They enjoy trying things and shake their heads when they fail. Life is an experiment and relying on past historic experience is totally ignored.

Did I remember to tell you that you are screwed?

You are not an engineer. You look bad when the sound is bad, they twiddle their dials and meters and really do not care.

They are looking forward to the next situation where they can pretend to know more than you and me.

Let me add that there are a few brilliant people in this field that you can trust:

Riedel Associates Is a wonderful firm, nationally known and respected by musicians.