hmm, well I'll have to pay attention to these inadvertent syncopations (I think that my chironomy is still…very idiosyncratic, I'll put it that way). Looks like I'll have to see if I stumble into this again one day.

OTOH the older accompaniments have their limits: the disaggregate neume is missed unless it's given an episema, which is not the case in the introit Ad te levavi for example, which Bragers misses, but Potiron doesn't.

Aha. I was wondering if I was thinking of an example from Le Nombre.

Also, what about a single note followed by a classicstristropha? (Again, something like a single note on La followed by the group of three on Do, or Re-Fa in mode II.)

There are a couple examples in upcoming offertories where Triors very clearly holds the isolated neume. I mean, maybe this is, and forgive mixing expressions up, in the weeds, missing the forest for the trees, but I have a very intelligent group of guys who are not afraid to ask questions such as “what’s the point, if I don’t aim to conduct?” (It helps the unity of the group, it gives a more lively impulse to the textual-musical relationship, it’s more musical than would be otherwise given the book in front of us, and, practically, because you might be unable to clearly see my hand at Tenebrae!); “do we follow this with the ordinary as it is?” (in theory yes; look at the bass and where it changes notes. Maybe not so much for now in practice!)

That's a rather nice recording. Mocquereau cites that same offertory near the end of his strophicus chapter and then argues forcefully for distinguishing between those groups and the bivirga/trivirga groups in the notation. But of course he was forced to accept the Vatican lack of distinction.

It is interesting that he is very clear that there should be a repercussion on each note, but then also turns around and says that it's impractical for a large and poorly trained choir, so one should just tie them together with vibrato. So he invents this rather lovely thing that should be a kind of lengthening different from both the mora vocis and the pressus, which he takes to be more forceful. I think Triors manages to pull it off quite well, because setting it off with a morula before makes it feel nicely ornamental and, of course, tied to the structural fa scale position.

If you want to conduct these with these little gaps, I think it would work well to use the hand or finger (and face) to show the tiny hesitation before going on to the strophicus. And then this is distinct from the example you posted about first, where the A is also an apostrophe and therefore light. Or you should try working repercussion in! In my experience if everyone is following the timing right (as in your watch-the-conductor thread) it works to have a mix of repercussion and holding (with undulation).

When I was looking up this example, I noticed that Dom M also postulated the possibility of an auxiliary/ornamental tone for the strophicus repercussion, which is almost exactly the same thing Dom Saulnier suggests 115 years later in his very last book.