in your first post you seem to have omitted the excellent Cappella Pratensis, but maybe you don't know their work. If not, do arrange to hear their recording of Ockeghem's Missa Mi-Mi at the earliest opportunity. It's yet another approach to complement the ones you mention, and as far away from the "English choral tradition" sound which characterises the Tallis Scholars and the Cardinall's Musick (and the Hilliard Ensemble and the Clerks' Group and the Orlando Consort, etc.) and which you describe as "trained" - trained, that is, in a certain way of doing things which may not have had a lot in common with how fifteenth-century "Belgians" might have approached their music.
I think it's fair to say that there must have been massively greater local variations in singing styles (as there still are in folk music), back then, than modern performances can do justice to. (Marcel Pérès suggests that "choral" folk music in Corsica and elsewhere might preserve a tradition closer to the vocal approach Machaut might have known than the "pure" tone favoured by Peter Phillips et al.) Obviously the "training" of a singer in those days would not have had the breadth or standardisation that a 21st century conservatory training provides; on the other hand, singers would have the depth and concentration of involvement in their "own" music that exists these days, if at all, only outside the Western tradition.
I don't know the Cappella Pratensis, and as ever their recording of Ockeghem's Missa Mi-Mi
is deleted wherever I've looked (you are good at doing this to me. The same applies to the Pellegrini Quartet's Nono/Beethoven CD).
I'm certain that the point about depth, concentration, and involvement is exact - I suppose that's what I felt the groups I listed managed to get closer to (or provide a kind of approach that allows for something of that to register, if only a kind of sonic image of it) than the English groups (although, clearly, those groups care about the music).
I'm sure there were plenty of local variations (standardisation of chant aside). And, of course, presenting the music as concert music (even if in a liturgical 'context') is to do something very alien to it. (Perhaps that applies less to Renaissance music, in that the work of, say, Josquin was highly prized as music
, and Ducal patronage enters the equation? The Missa Hercules dux Ferrariae
, for example).
What Peres theorises is always interesting, and I love the results. Sadly, the one time I went to Corsica in the late 80s I heard no folk music.
Off-topic, but I have a more general problem with 'singing' singing (often in Lieder). But that's another issue.