This is a classical example of semiological chanting.

I don't have access to spotify, but if I found the right youtube video, it appears to be Alleluia Justi epulentur.

It appears in the Common of Saints, specifically common of martyrs outside of Easter. It might also be used for a weekday Mass at some point throughout the year, but I'm not sure.

@trentonjconn Thank you so much!!!

I second Matthew here. This is a perfect example of the classic Solesmes method (Mocquereau/Gajard) as it has since come to be developed at Fontgombault and is taught in the Laus in Ecclesia series. Also noteworthy (something that has come up fairly recently in the forum) is the rather understated organ accompaniment.

Thank you for sharing this. It's quite a beautiful recording.

@Charles_Weaver So, I have been LOST in the rabbit-hole of a recent-ish debate between you and Ostrowski (sp? is he the same as FSSP on here?) and have been trying to catch by ear the difference between semilogical interp. and "classic solesmes" (and, I think I have been understanding that "mensuralism" is a sort of half-way between the two? still to the space of metronomic counting but with more free-form accentuation than just twos and threes?) -- and I was *thinking* that what I was hearing (based on the first replies to my post) that this (Fontgombault) (thanks @MatthewRoth)! *was* semiology interp. But's it's not? Can someone here link me to a very "semiological" interp of something? I guess I still don't know what that *sounds* like....

Where I am, if you search "Chœur des moines de l'abbaye de Fontgombault", you'll get whatever is available here for streaming.

The Assumption album is perhaps their most famous. They've done Easter, Pentecost, Corpus Christi, the Immaculate Conception, (back when they did the Novus Ordo at Fontgombault) the solemnity of "Mary, Mother of God", Sacred Heart, the dedication of a church, the Requiem (according to the Roman rite and to the Benedictine version, which has slight differences in the chants) and two Marian albums (those are what I have found online; there are more which can be purchased on CD).

Jeff Ostrowski does work for an FSSP-staffed church (I see where the confusion arises). The interlocutor of Jeff and Dr Weaver who also posts here is Patrick Williams, who is the advocate for proportional-style chant. As you've perhaps discovered, Jeff prefers the Vatican Edition and its rhythm; Dr. Weaver sings in the Solesmes (Mocquereau) style and sometimes uses the Graduale Triplex, thus singing in a way informed by the work of Dom Eugène Cardine (whose book Gregorian Semiology is sort of the forefront of a new look at the manuscripts, in tension with but certainly not opposed entirely — not from Cardine anyway — to Mocquereau's method).

That gets us to semiology: in essence, it's not a method. Rather, it's a new and particular attention to reading the manuscripts or the copied neumes of the same and singing accordingly.

Edward Schaefer has posted some recordings. This Kyrie is mostly in a Solesmes style (The Kyrie is sung 2-2-2, and not 3-3-3, because it's for the NO). , and it's too simple to indicate much of anything, but the bistropha is always treated with the repercussion of the second note by someone who is more semiologically inclined. The same is true for the tristropha, the pressus and the oriscus. Mocquereau felt that while this was ideal, it would be too hard to do for most groups and singers.

The same is observed here with the Hosanna, Filio David of Palm Sunday. Dr. Schaefer studied with a number of people who mostly fall in Dom Cardine's tradition; there are other interesting examples of semiological-style singing like Marek Klein's Graduale Project that move slowly but surely from Solesmes.

We can even compare Monsignor Turco's singing of the gradual Laetatus sum with Klein's. And for good measure, the women of the Chœur grégorien de Paris.

There are semiologists who stick to the Vatican edition, including the Solesmes editions of the same (for convenience?). Others use their own editions, like what Royce Nickel does with the Graduale renovatum, or use editions such as the Graduale novum.

Mensuralism "just" means that there's a beat in the rhythm (whether or not you indicate this in conducting) and that we can basically measure the note values. Dr. Weaver goes into a bunch of different historical and contemporary approaches to mensuralism, from the Renaissance and post-Tridentine (Baroque or Counter-Reformation) perod to the nineteenth century to those referenced today who were also interested in the manuscripts, and later theorists, but drawing different conclusions from the Solesmes monks. So that means there's "just" a beat for some; for others (what is called proportionalism), the notes are in a 2:1 proportion of long to short and that the manuscripts indicate this; finally, others are not as strict about the 2:1 proportion and have other figures — tuplets and irregular proportions would be key characteristics.

Cardine's disciples and Mocquereau wouldn't have proportion (the rhythmic signs and long neumes are attributed to nuance in interpretation, not a ratio of long to short) and even more importantly they wouldn't subdivide the punctum. It is a fundamental unit. There is no subpunctum, so while you can transcribe chant with eight notes (and quarter notes if one wishes to do so for certain notes), the "one" beat is multiplied into units of twos or sometimes threes, and those combinations form the melody. It's indivisible.

Also, note that the terms syllabic beat, shortened beat, and lengthened beat are used in the English edition of Cardine's Gregorian Semiology. So, there is a beat (ictus) in the Solesmes method, a beat (tactus) in the mensuralism of Van Biezen, and a beat (valor/tempo/temps) in Cardine's semiology too.

My attempt at the Alleluia Justi epulentur under discussion, according to the Graduale Novum and (somewhat unusually for me) the St. Gall neumes:
https://youtu.be/71zaqWpRu1M