I thought he left an endowment to ensure that his the mass would be sung regularly as part of an annual memorial ceremony for himself and his brother.
If that's right he was trying to make his music live on after his death, and he would have known that it would be presented in different ways, subject to different singing styles. He knew that singing is a living practice, and that the score doesn't determine what a performance will sound like.
That's why using Corsican ornamentation and timbres is perfectly consistent with Machaut's musical intentions: by letting the Corsican singers respond creatively to the score, the mass gets plugged into a living tradition which goes all the way back to the 14th century in fact.
As far as I know there was no such endowment and regular practice associated with the Tournai. This could partially explain why Pérès treated them so differently.
I managed to download the booklet with Schmelzer's notes and have decided he is acting out his own agenda which is not supported by the available documentation. He gets his ideas from art criticism and not musicology, certainly not from musicology associated with Early Music.
1. We do not have a copy of Machaut's will and the information regarding an endowment is based upon the transcription of a bronze plaque that was inside the Reims cathedral until the 18th century (the plaque itself no longer exists, nor are Machaut or his brother buried in the cathedral). This text alludes to an amount of money collected by friends of Machaut (probably other canons) and made available for a short dedicatory prayer to be recited prior to the regular Saturday Lady Mass. We have no evidence that the mass sung was even Machaut's.
Schmelzer makes much from the assumption that Machaut intended his mass to be performed after his death. Schmelzer creates an entire mythology around this idea using highfalutin words such as "euchrony" to posit an attitude he attributes to Machaut (and one you seem to have accepted whole-cloth) that future generations have the right to reinterpret Machaut's mass as they see fit, because that is what he wanted. Smacks of a Regietheater approach to Machaut.
2. La Messe de Nostre Dame of Machaut appears in notation in five of his collected works. In only one of these is it entitled "Messe de Nostre Dame". In one other it is merely called "Le Messe" in the other three it has no title. Hence there is scant evidence from the notation in his collections that Machuat considered his Messe as a Lady Mass, certainly not "the Lady Mass" sung as a memorial to himself. The more substantial evidence linking La Messe
to the liturgy of the Virgin Mary is the fact that all of the chants Machaut used were associated with the Lady Mass.
Regarding these chants, Schmelzer writes that Machaut "provided the plainchant of the ordinary for the Lady Mass with a previously-unknown affective polyphonic trope
." There are at least five chant variations for each of the Lady Mass sections. Machaut used the most common and assigned it to the tenor, where it would normally be placed, and added his isorhythmic counterpoint around it. There is nothing "previously-unknown" about this procedure. I have no idea what he means by the qualifier "affective polyphonic trope." Once again Schmelzer assigns an idea to Machaut wishing to cause some kind of emotional reaction among the audience based on nothing other than the pile of speculation Schmelzer has imagined.
In order to support his contention of how strange the Machaut mass would sound to the singers (and presumably the audience) Schmelzer writes, "Rather than breaking the tradition, he cracked it, offering his colleague-singers a musical diagram (the word Schmelzer uses instead of notation) in the way a 'trickster' might do - radically transforming
what they were used to singing according to the tradition and to their skills."
Well, I 've check all of my books, including three on Machaut, and two on Medieval performance and notation which all have sections on the Machaut mass, most which address the chants used and Machaut's treatment and nowhere did I find anything alluding to Machaut breaking with tradition. To the contrary they all stated that Machaut's mass was entirely traditional and in fact copied ideas from previous mass settings.
My conclusion is that Schmelzer is as nutty as a fruitcake.