For those of us uncool kidz who are not inside the inner sanctum of current experimental chant practice, could someone give a broader context to appreciate this?

That alleluia gives me chills. I can't put my finger on it, but I feel it in my bones. I suspect that this is muuuuuuch closer to what early chant sounded like.

what early chant sounded like

I suspect early chant (may have) sounded like this in one locality, and quite different in another - just like Beethoven sounded one way in Vienna in 1822 and another way in Chicago in 1922 and another way Tokyo in 2022 - which is all good in my book.

What works in a parish setting is another question, though.

If you speak French, the man who runs L'École grégorienne has a fantastic video explaining why they interpret things the way that they do, and why they do not sing according to the solesmes method. https://youtu.be/0Im2hzBRRiE It really is worth watching. Frankly, I find his arguments convincing.

Not least of all, the principal of working back from living traditions, rather than trying to reconstruct a theoretical interpretation based on 800 year old books seems sound to me.

He also demonstrates how some of the decisions taken by the solesmes monks when editing the Graduale Romanum do not accord with various manuscripts, and why alternate semiological interpretations are legitimate.
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Rich_enough, there is little doubt that there were all sorts of 'valid' interpretations of chant back in the day, and they would have all be localized. (One could rightly pose the question, 'how could this NOT be the case?') Europe was/is awash with multiple rich musical traditions, and each language has its own rhythm and manner of singing; all of these things quite naturally bleed into musical interpretation and would have surely influenced chanting too. Compare the natural stresses that are put on vowel sounds between English and Spanish, for instance. (As a silly example: comPUTer vs computaDORa) Some ancient monk chanting in England would very likely naturally intuit certain neumes a little differently than a Spaniard of the same vintage depending on where they fell on certain words. Granted, they would have all been schooled in Latin, but only as secondary languages, so natural biases would still come to bear.

I have watched some of Labriolle's videos. I find his chant both beautiful and problematic. Beautiful, because it is, well, beautiful (I especially like how he has restored the use of the falsebordone in his schola); problematic because there is some kind of archeologism in his work. By the way, when he criticizes the Solesmes method for it being imposed from the top with little respect for the local plainchant tradition, he tends to do the exact same thing: his chant, while beautiful, cannot be linked to any tradition (not even the Corsican chant, which he rightly loves - even so, Lyons has a tradition of it's own, which should not be replaced with another).

Please note also that Pérès and Labriolle are not exactly doing the same thing.

Also, I wonder: in a place where there is no chant tradition to speak of, where Gregorian music arrived with the Church in the 19 or 20 century, what is to be done? Must we sing only in the Vaticana style, despite its faults, if that's our fifty-years-old and fifty-years-forgotten “tradition” ?

I would say yes.

One thing I like about Labriolle though, aside from his criticism of the 'Solesmes' method, is his insistence on the old plainsong tradition (in some cases, maybe not so old, but definitely traditional).

On the whole, I believe he is doing a very good job.

I like Perez' work, and I think it is a natural reaction to the 'prettified' Solemes tradition. One must say that chant must have been performed a thousand years before the notation even developed.
However, there is simply NO way that anyone can say what it sounded like. EVERYTHING is guesswork.
I feel that way about drones. Correct me if I am wrong, but there is not much evidence of drones being used with chant - and the changing of the drone according to modal inflection is complete guesswork. Fauxbordon and Leonin and Perotin are extant, but that is a later development...
This reminds me of the many wonderful recordings by the Hesperian ensemble and Jordi Savall. I remember when I was just getting into early music, I heard a 20 minute recording of a medieval piece that featured half- a dozen instruments, percussion, voices etc. I though: "man, I just have to find that score!" well, when I found the 'score' it was one line of music four measures long! It was all made up.
This is not to disparage any of these fine artists and their work.

It's not difficult to posit that what was notated in the ninth and tenth and modern eras was a notation of what had been sung long before. I don't think that the work of Leonin and Machaut appeared in a vacuum. We have enough improvisatory, even imitative chant-polyphony even into somewhat later in time. Faburden and other four voiced forms are examples of an improvised chant form which is practiced even today and doesn't need notating. Thinking that the earliest notated music rose out of thin air is not very thoughtful of human ingenuity and historical processes. That would be like believing that Homer's epics did not exist before they were written down - no, they were written down long after they were passed down to this day. Similarly, the backwards cultures in parts of India have passed down in cantilation the life and conquests of Alexander the Great, who made a big impression in these various peoples and their villages. Sung, these 'gestes' are treasures of their tribes and are defining aspect of their people. Yes, it would be very nice if we could know what pre- Bell Canto sounded like, but Peres and jordi Savall are paving the way.

However, there is simply NO way that anyone can say what it sounded like. EVERYTHING is guesswork.

Challenge accepted! There actually is a way. Not to 100% certainty on every single vocal inflection of Lyon, France, or some other city in Europe, but to nigh-100% certainty on musical details. It requires a 'holistic' (gotta love that word with all its baggage) approach to the analysis in order to figure it out, by synthesizing a number of existing methods.

The following, for instance, is easy to verify.

1. The vocal style in the ninth century among the Italians was heavily legato, while that of the Franks and Germans was not, because Joannes Diaconus says so, once you know how to interpret his musical terms.

2. The tempo of Roman chant is determinable from a paragraph in the Commemoratio brevis that elucidates the relationship between simple and solemn tonage.

3. The contours of the Late Roman (Old Roman) chant, after doing the needful parallel parsing of the chant's rhythmic beats, reveal its stylizations to be neighboring and sliding grace notes, very smooth, like wine and chocolate.

You combine these three facts, and the general Roman chant sound is completely reconstructible, and it does not have any evidence or any room for the kinds of time suspensions that Labriolle and Peres take to insert Middle Eastern shakes. (Organum on the other hand ...)

Note, the above is nowhere nearly enough to ascertain the authentic melody, but it does give the amateur musicologist the tools to tap into the cognitive framework that's required to make sense of the oral tradition behind the chant, a topic that could earn you multiple PhDs if you feel inclined to study it.

Coemgen –

I am sympathetic to your analysis, but I am sincerely curious how one can determine what is orally transmissible, insofar as a Carolingian mind was not burdened by all the books it had consumed, theoretical comprehensions of computers and relativity and Walmart, and every song in the Top 40 since 1965. People from isolated cultures today seem to have much better memories, capable of retaining epic poetry and vast numbers of songs.

I am sincerely curious how one can determine what is orally transmissible, insofar as a Carolingian mind was not burdened

There is a lot of literature out there on orality and transmission, but none that I would recommend for easy access. Most is either too advanced or too generic, or tends to focus on how the music was transmitted rather than how transmittable it was.

Oral (aural really) transmission is not quite as mysterious as you might suppose. The eighth-century Romans did not have superhuman memory, just like Byzantine, Coptic, Ethiopian, and Syriac cantors today don't have superhuman memory. Nor did the Carolingians, who were shown by Levy to have depended on neums going all the way back to circa 800, likely including the 790s as well when the supposed Carolingian archetype was likely written. Moreover, there are large pockets of pitch corruption in the Graduals of Modes 2 and 5 that can't be explained any other way than by the Carolingians mislearning the pitching of Paleo-Frankish neums which they themselves wrote down and misinterpreted before they had memorized the chant properly.

If someone someday ever publishes the melismatic chant perfectly reconstructed, you would be blown away at how easy it is to pick up if you have Byzantine or Coptic chant experience, because

1. The rhythm has a metrical hierarchy of beats, even when the emergent meter is broken, and that gives the mind a sort of organization system, holding the rhythmic units together in a collection of symmetries that the mind can latch onto easily.
2. The motivic contours and melodic momentum drive the cantor through certain patterns of pitch space, what I call 'motivic rudiments', such as "B-C-A_-G_" that repeat themselves so often that they dictate the composition itself.
3. The formulas take on patterns, not just the cadencing but whole phrases, both in the syllabic and melismatic styles, that become predictable, so that 50 formulas feel like improvised variations of only 5 or 10.
4. The goal toning and compositional 'rationale' is in many cases extremely simplistic once you take a birds' eye view of the chant, such as the D-C-F-D phrase structure of the Mode 2 Tracts.
5. This all makes memorizing multiple thousands of songs much easier, since the shared material is only about 40 to 100 hours worth of total music, and the rest is "com-posing" / "compositing", putting together.

The Peres interpretation has none of that to hold it together, so the mind cannot latch onto the 'structure' of the music and retain it. Try yourself to memorize all of the Ensemble Organum albums note for note, time for time, and reproduce them without

- speeding up past the singers
- speeding through a note that you should have held
- steering the course of motion to the wrong pitch
- confusing motives
- crossing from one chant into another
- accidentally singing a Gregorian motive
- messing up horrendously at the sheer chaotic inconsistency of it all

You would have to listen to each album repeatedly many times to get it right. Amplify that to a couple of thousand chants without any formulaic system to tie it together (Peres' interpretation of the same motive varies from chant to chant), and you'll see how impossible it would be for the Carolingians to receive and transmit Marcellian chant as a tradition.