Father -

Relevant to number one on your list, chant is a sacral, an hieratic musical language which in its origins and history was devised and used, set apart, through the centuries for no other purpose than to grace Catholic worship with its beauty and 'other worldliness'. There is no other music like it. It is the Church's musical language and is heard only in the Church. By a sad irony everyone knows this except modern Catholics, owing to its deliberate (and illegal!) suppression following the recent Vatican council.

By sacral or hieratic I mean that by its unchanging musical language through the centuries it has acquired, if you will, a sacral, hieratic character, a sacred patina, much like that of the verbal hieratic languages of Latin, the various eastern languages, Old Church Slavonic, and even Old Church English (the language of the Anglican BCP).

Chant can be heard and loved by Anglicans, some Lutherans, certain 'high church' Protestants, and even those who practice 'meditation', but has been exiled by most Catholics who perceive it to be a holdover from pre-conciliar times rather than a part of our Catholic patrimony that lives yet today and was commanded by the council to be preserved and fostered.

I shant go into the horrors of most of the music which has replaced chant by people who thought they needed something 'modern' for 'modern times'. There is nothing 'modern' about the sacro-pop, sacro-jazz, and sacro-this and that music heard in our churches. The melodic and harmonic vocabulary of this music was, in the world of serious music, left far behind long ago and can lay no claim to modernity.

There are really two issues here. The propers are texts which are set to music. Chant is a musical form.

I think that the use of the propers is a fairly easy “sell.” They are texts which the church assigns to the mass. They are almost all scripture or close paraphrase of scripture. Using the propers both conforms the parish liturgy more closely with the universal church and increases the amount of scripture used at mass.

In terms of the use of chant by the parish, that also is a matter of education. While the church doesn’t exclude any worthy musical form from the mass, she has repeatedly said that chant is the musical form which best suits the mass. Your parishioners should learn this. Bulletin articles or short talks before mass placing chant in the context of Vatican 2 and the implementing documents may be one means of education.

Putting this into practice becomes a matter of learning basic repertoire. The Lord’s Prayer is something that many congregations learn and sing with gusto. There are the Latin Chants that Paul VI gave to the church in Jubilate Deo. There are now the ICEL chants.

Finally, talking to people in the pews And finding out what can be done to increase their participation in the singing might also be helpful dialogue.

1. Why chant? Because the texts are paramount. They have not been selected or translated with a metric structure and should not be pushed into one, and preferably not paraphrased into one.
2. Fitness of form. JonathanKK succinctly, and Dr Mahrt in detail, explain this.
BUT we then need to ask whether the form of the OF is the traditional form in which the Graduale Romanum was developed. I would say it is not, and therefor we should adopt chant of a different form. There are serviceable resources available (Rice, Weber, Kelly, Bartlett, Ainslie, ...) in the interim while we spend two generations rebuilding.
NB the OF requires three Processionals, of different forms, Entrance, Offertory & Communion. And the chants between the readings are Responsorial Psalm and Gospel Acclamation which are totally and completely different from the EF structure.

How is Weber different in "form" beyond language?

Father, I recommend you speak with Father David Carter, pastor of the Basilica of Sts. Peter & Paul in Chattanooga, Tenn. He has done a masterly job of preaching about sacred music and liturgy in order to help the congregation understand the various changes and improvements that have been made over a period of several years. The parish produced excellent handouts as well. And he has a fantastic music director, my friend Maria Rist. Parish website: https://www.stspeterandpaulbasilica.com/

You said that "chants of a different form" were required in order to fit the NO, and listed them as examples of what you meant. How are they different beyond the language used?

I understood that part of your post, but don't get why the GR Propers don't work for that in your eyes, and what is needed to replace them in the NO.

I should add that GR propers do not work all that well, for the reasons francis gives, they were developed as ovelapping with the celebrants action and they were no longer used as processional chants.
Also if this expresses an order of preference :-

GIRM§48. This chant is sung alternately by the choir and the people or similarly by a cantor and the people, or entirely by the people, or by the choir alone.

I think I can safely say that congregations capable of satisfactorily singing GR propers are a rarity. Psalm verses, to a simple Office/GS chant (or Murray, Bevenot, Kelly, Weber, ) are about the most one should expect. For some reason GS suggests giving the antiphon to the congregation, no wonder when I talked to my former archbishop about using propers he said "Yes, I know we should, we tried it and it doesn't work"

With Squarenote and / or Propers Tool and perhaps, http://www.gregorianbooks.com/propers.html almost any musician can sing the Propers. While some of the Propers are tricky, most are able to be sung with a little practice and few are easy to sing. It is not talent that is lacking in most places it is willpower.

Oh and if you are looking for Musicians, you may find them by looking to see who has cotton wool in their ears! One of our chant directors in London formerly hid in the congregation, until we turned up with a chant choir to sing at her parish.

You can very easily SING the music of the VO at the NO, but that is not the essence of a more basic and central issue. You could also (and some get close) play In-A-Gadda-Da-Vida there too. The real problem is that with the right personalities, it is entirely possible to do so. The chant is not designed to fit inside the NO. It is organic to the VO. It grew inside of and is native to the VO.

It's the parable of the old wine in new skins all over.

In his book, Demain la Liturgie [The Liturgy Tomorrow], Father Gelineau commented with commendable honesty, and not the least sign of regret:

Let those who like myself have known and sung a Latin-Gregorian High Mass remember it if they can. Let them compare it with the Mass that we now have. Not only the words, the melodies, and some of the gestures are different. To tell the truth it is a different liturgy of the Mass. This needs to be said without ambiguity: the Roman Rite as we knew it no longer exists [Le rite romain tel que nous l'avons connu n'existe plus]. It has been destroyed [il est détruit].

I should add, Thank God, that the Roman Rite DOES still exist to the chagrin of those who would like to have banished it once for all, and it is increasingly being sought out by the flock.

@Schönbergian

While it is possible to sing the GR propers at the NO Mass, and we have plenty of examples of this working. The various rites of Mass used in the past had music as an integral part that grew up with the texts. With the modern rite, those that invented the texts and liturgical arrangements did not give music as an important part, and so it has been generally overlooked. (It is all very well writing about the importance of the ancient chant, but actions speak louder than words!)
After all these years we still do not have a full set of music for the modern Office and Mass! How many Propers have been created over the last 50 years with no thought of how they would be sung?
While it is great that talented and imaginative people have produced music for many texts and have a full sung Mass on a regular basis, for others it is a difficult path to tread.

Father, one tactic you could try is to point out how every other rubric for the mass is (I presume) followed. For example, you don't make prayers up at the beginning of mass, you say the collect. The same is supposed to be true of the opening "hymn": you are supposed to sing the introit; a hymn only qualifies as a substitution for the correct thing, and even then, only as a last resort for option iv in the GIRM. Quite literally the very last option permitted by the GIRM is what has become the standard practice.

You can also appeal to the beauty and symmetry of the liturgy when propers are used. They are related to each other and to the readings at mass, so the whole proclamation of the gospel is enhanced even further and the thematic veins of the liturgy become even more apparent.

If singing them won't go down too well right at the beginning, perhaps they could be recited or simply used in parallel with the current musical offerings. Recite the introit before the opening hymn or sing the opening hymn up until you reach the altar and then chant the introit. That way it doesn't totally supplant what they are used to.

@CatholicPriest: here is a video series I made, to be shown at churches, to educate parishioners in a non-threatening, low stakes way, without losing any of the substance of the church's teaching: https://ctk.cc/what-is-sacred-music

Here is another thing that I would like to say:

In contrast to the EF where in order to have a sung Mass all propers must be sung, in an OF context, it is possible to sing a single proper. This means that in the OF, there is no absolute need for intermediate steps such as simplified/Rossini propers, English propers, hymn tune propers, etc. One can simply prepare a Gregorian proper, and sing it at Mass.

[Digression: I tend to think that these intermediate steps are to be avoided, because there is no sense in accustoming people to singing a new intermediate step if you will only be replacing it later on.]

With my schola, the very first full propers that we did were introits. I think the first three we did were at long intervals: Puer natus at Christmas (described by our chaplain as a specially beautiful piece, which he requested that we learn), Signum magnum for the Assumption (which I knew because I had done a polyphonic composition on that text), and Gaudeamus for Our Lady of the Rosary and All Saints (the mode 1 incipit just begs to be sung).

*****

If anyone wants to know, the rest of the progression was:

Later, I think we pecked away at an odd communion now and then. But when it came time to shoot for something every week, I decided that we would go for introits. The introit in my opinion is a better first choice, because it is like the figurehead on a ship: immediately recognizable, and standing at the head of what follows. So we labored through introits every week with full choir.

At some point, a few of us began to add the communion, and then some offertories. Soon, this got to be a regular thing. The other trend was that it stopped seeming so critical that everyone sing the introit. So it got to be that everyone would sing on what they were able to handle. May I say, we had not much rehearsal time, and what we did have was directly before Mass. I was not a good manager of such things as requiring attendance - or I would have had no singers. My strategy was rather to have everyone willing to help in any way do as much as they were able.

Keep fasting forward... at some point, we were taking pot-shots at graduals and alleluias. At this point we had a setback, Father requested that we not do the full graduals and alleluias, because we were not having sufficient success. But such a restriction of its nature could not last long, and I do not think it was many months before we were back at it.

I think it must have been spring 2013 (I do not have these things written down), we sang all of the full Gregorian propers for the 1st Sunday of Lent, and did not look back. If no one else could sing a certain chant, I would sing it solo, because by that point it was more important to maintain consistency in the use of the full propers than to avoid solo singing. This became apparent on the first and only occasion that I tried going back to a Rossini introit for the sake of having multiple people sing it: when you are genuinely accustomed to full propers, a psalm tone proper sticks out like a sore thumb, it is just lame, it has no musical content.

We did not miss a single proper thereafter, and we always sang for all Sundays and all Holy days of obligation in the entire year. Of the nine years that I directed this schola, that would have been the last four that we were basically doing full propers.

*****

May I add in closing a point of which I am reminded:

It is not sound practice liturgically for the choir to take the summer off. Sung Mass must be maintained throughout the entire year. I suppose that you may if you like have a "fancy" choir which is seasonal. But the heart of the singing is the Gregorian chant, and this it is entirely possible to continue year round.

Anything to the contrary notwithstanding.

Read Music and Morals, by Basil Cole, OP
Treats the dichotomy between sacred and secular domains. spiritually healthy and unhealthy music.

I also watched the videos and they are well done. I was particularly happy to see that it was being presented by a musician and that he has taken the time to educated himself enough to easily explain the need for Sacred Music in the Mass. Well done.

Wow. Many thanks to those who provided links and suggestions!

@ M. Jackson Osborn : they were only released about a month ago, so that remains to be seen. I've heard from directors and priests in a couple dozen places who are going to be using them, so....we'll see!

I have provided a link to sergeantedward's video series to my choir members. Several have already told me how much they learned from the videos and that they never before had heard some of the Church's teachings about music at Mass.

Same. I was particularly surprised when I received a (somewhat odd) email from one of my more liberal choir members who is less keen on the changes I've been making. I didn't even think this person would take the time to bother watching them, so it appears a little miracle has taken place.

I've also written a bulletin column which mentions this series and links to it, so I hope it will receive broader reach in the parish in a week or two's time.