The reality in some places that I know is: people who can't read music, a dearth of people with even basic keyboard skills, congregations that do not understand when they should sing, no pipe organs or even simulacra of any merit.... Some of the views proffered earlier about the need for singers to commit, rehearse at certain times in the week (etc etc) seems very out of touch with the realities that I have witnessed in some places. A new set of Mass Propers every week may simply be impossible for some choirs.... The full propers may always be beyond them.

So, your position is that people who can't read music, can't attend rehearsals, and won't ever be able to sing full propers need the opportunity to sing psalm tones at High Mass because it would be an enrichment. Where exactly does the legislation of the 1962 Missal say that rank amateurs have business singing the Mass? I must have missed it. Why not just sing easy and familiar hymns (Latin or vernacular) well at Low Mass until competent cantors are available? Save the psalm-tone propers for when it's an obscure third-class feast and a High Mass is scheduled on a workday and needs to be finished in 45 minutes. Then you may have some justification, but not at the principal Sunday Mass week in and week out for decades.

if you start the introit on a Sunday immediately when the celebrant puts the chasuble on after the Asperges

A point of clarification: the introit should not be sung until the priest goes toward the altar according to the rubrics of the Gradual. It is an entrance chant, not a vesting chant. Formerly (before 1908), it wasn't begun until the celebrant had reached the altar.

To be fair the timing is also tough. We begin when the priest is about to turn around but someone might get stuck if at a solemn Mass his maniple doesn’t tie correctly.

Yeah, and if you can’t do weekly propers do one full Mass a month; the rest should be dignified low Masses.

So, your position is that people who can't read music, can't attend rehearsals, and won't ever be able to sing full propers need the opportunity to sing psalm tones at High Mass because it would be an enrichment. Where exactly does the legislation of the 1962 Missal say that rank amateurs have business singing the Mass? I must have missed it. Why not just sing easy and familiar hymns (Latin or vernacular) well at Low Mass until competent cantors are available?

No: my position is that a congregation should not be denied the opportunity to learn all the plainchant Ordinaries (nor be restricted to hymns) and servers should not be prevented from training regularly and learning the ceremonies of the solemn liturgy because there are not sufficiently trained singers to execute the full propers.

The sung liturgy should not be some kind of 'reward' for a particular stripe of singer; it belongs to all the faithful. Neither should Low Mass be a 'punishment' because the errant singers cannot sing the full propers of the Graduale.

In any event, there is nothing in liturgical law that takes the position that psalm tones are to occur by exception only (etc).

A point of clarification: the introit should not be sung until the priest goes toward the altar according to the rubrics of the Gradual. It is an entrance chant, not a vesting chant. Formerly (before 1908), it wasn't begun until the celebrant had reached the altar.

Thanks for this clarification. Yes, that's when I stop my prélude à l'introït and then I walk over to the schola and start singing when they move. But as we all know, there are many ways in which I don't measure time as precisely as you!

The people who don't know how to sing mass won't know how to sing Vespers either. Now we've got them struggling to learn, on their own, an entirely different liturgy, famous for being complicated to the uninitiated

But a cantor can. And he can more easily teach someone. Also, there are oodles of resources maybe even more so than for the Mass. The 1962 is hardly variable anyway. I believe only Holy Cross and the Lateran interrupted the Sundays after Pentecost from July to November. I know that Saints Peter and Paul did, but many choirs and musicians take a break around that time anyway.

At some point you have to embrace the suck and power through it.

The sung liturgy should not be some kind of 'reward' for a particular stripe of singer; it belongs to all the faithful. Neither should Low Mass be a 'punishment' because the errant singers cannot sing the full propers of the Graduale.

Then they have to get better! It’s not a reward, but you don’t a a right to a sung Mass, and psalm-tone propers are cheating the people of their inheritance as well.

In any event, there is nothing in liturgical law that takes the position that psalm tones are to occur by exception only (etc).

Meanwhile the law is perfectly content with the current norms of the NO. The law also doesn’t explicitly prohibit clown Masses (you have to piece together the law to do so, really). But more seriously yes, it does. The psalm tones are exceptional, but hey, just like EMHCS, they have a way of sticking around permanently.

Anyway it’s hard to prove the negative here.

But I actually am serious: do weekly Vespers, and then do a monthly sung Mass with full propers. Or quarterly even.

There are so many resources available now that aim to address the situation being described here: CMAA, CC Watershed, countless youtube recordings of the propers. The authors of the sacred melodies didn't know how to read music, so I don't see why that should be an insurmountable barrier at present. A lot of us pour out significant chunks of our lives educating people in how to sing chant. Culture takes a long time to build and can be wiped out quickly. Ora et labora!

While well intentioned, the fruits of self-directed online training have the potential to be lemons. Far better to hear a well-executed psalm tone than the butchering of the Graduale by the inexperienced or inept. I agree with you that culture takes a long time to build and prefer to see slow, steady and incremental positive change.

Although it is true that the authors of the sacred melodies did not read music, they had the benefit of living in religious institutions where the plainchant repertoire was at the core of their lives. That is a fundamentally different proposition to a small group of singers coming together potentially once a week for a limited period before Mass. The two aren't equivalent to each other. The context could not be more different.

a congregation should not be denied the opportunity to learn all the plainchant Ordinaries

All of them? Seriously? Rare is the congregation that can maintain a repertory of more than three or four Ordinaries from year to year.

In any event, there is nothing in liturgical law that takes the position that psalm tones are to occur by exception only (etc).

You demonstrate a legalistic attitude, focusing exclusively on what is tolerated to the detriment of what is beautiful, artistic, and becoming. The essential function of the Gregorian psalm tones is to get through a text efficiently, in a fairly straightforward tone that corresponds to the mode and tonality of the associated antiphon. They do not exist in order to sing a text in a more solemn or protracted manner, rather the opposite. Put another way, they are a means of textual recitation rather than proclamation. Yes, you are correct that there is nothing in liturgical law prohibiting them, but that misses the point that the rest of us here are all trying to make.

If you look on p. [1] of the Liber Brevior, the following notice appears as a footnote:

These abridged chants are intended exclusively for churches where it is not possible to properly execute all the melodies of the Roman Gradual and for which a simple melody of the Sacred Texts is tolerated (S. C. R. N° 3697). Where there are Choirs sufficiently trained, the official Chant of the Gradual must be kept.

The same notice appears in French on page [1] of Chants abrégés. The CMAA scan of the Rossini 'Proper' of the Mass adds it on the title page. What does SCR N° 3697 actually say?

On the occasion of publishing a work entitled Manuale liturgicum ad usum Fratrum Minorum Sancti Francisci Capuccinorum, some questions arose among the rubricists of the same Order regarding the particular rites or rubrics contained in the same work. In order to thoroughly resolve such questions, the Reverend Father Fra Bruno a Vintia, Procurator and Commissioner General of the Order, deemed it his duty to propose the following dubia...
Dubium V. Can the practice of singing the Mass in a quasi-psalmodic or semi-tonato manner be tolerated?...
To V. “It may be retained.”

I don't have access to the manual in question and can't comment on the specific style of quasi-psalmodic or semi-tonato recitation permitted to the mendicant friars of the Capuchin order. In my opinion, the citation isn't especially pertinent, but DMS 21c is crystal clear:

But if for some reason a choir cannot sing one or another liturgical text according to the music printed in the liturgical books, the only permissible substitution is this: that it be sung either recto tono, i.e., on a straight tone, or set to one of the psalm tones. Organ accompaniment may be used. Typical reasons for permitting such a change are an insufficient number of singers, or their lack of musical training, or even, at times, the length of a particular rite or chant.

So, it is permissible to psalm-tone or monotone the text of the chant if there not enough sufficiently trained singers to execute the full chant properly, or if there is an occasional need to speed things up. But to introduce a High Mass to the parish schedule with the notion of using psalm-toned propers for decades seems wrongheaded, even more so if part of your intention in chanting the proper offertory to a psalm tone is to leave plenty of time to sing several stanzas of something from Piae Cantiones or the like. As I and others have already said, it would be better to wait until you and your priests can sing the Mass properly then schedule High Masses at manageable intervals. Then if and when you're short on good singers, it's acceptable to use a psalm tone.

Rare is the congregation that can maintain a repertory of more than three or four Ordinaries from year to year.

We imposed more than that, but we sing some so rarely or only intermittently throughout the year (e.g. a lot of Mass IV in May and in June) that they don’t sing beyond the Kyrie. But that’s also fine. I’m happy to have fifty people at a weeknight high Mass.

The Capuchin liturgical praxis before V2 ought to have been deprecated to be frank.

But also, again, even with the obvious ordinaries. You’ll have a lot of Mass XI especially if you do the 1962. (After five years you’ll start to want to do the anonymous Missa ferialis and substitute another chant Gloria for variety in July and into August…). Mass I? It took us a good five years to feel comfortable with it. I’m not always sure that we’re there with XVII.

That certainly can’t happen if Sung Mass is the exception rather than the norm.

You just have to put work in that you’re not willing to do apparently. I speak from experience: people need to get used to the idea early of signing full propers. A culture where you use psalm tones for the sake of having a high Mass, and for the sake of the servers, is not what you want. (Besides the servers need to get used to the idea of the gradual, alleluia, tract, or sequence being long and managing the movements during those chants.)

It doesn’t take decades, but for it to take years; you have to put in work, and you’re not encouraging people to put it in. The robust congregational singing is, in part, because there is balance. Not only are they not expected to sing everything, and that which they don’t routinely sing is far too complex (it is meant to be received so that they might contemplate), they don’t have to sing every last bit of that which they are invited to sing.

And sometimes they just don’t participate vocally despite it all. You cannot account for that much.