Exciting work to be preparing, good luck! It's very tempting to dig in deeply but I don't have time right now. Generally it looks to me as if Schrade was using the 'squeeze the neighbor and leadingtone' rubric, rather than any good reason. The Bbs I see no need for (though the B in each case would be sung low, a small whole tone above the A). Edit - additional comments not relevant to the Gloria deleted.

If your preparation goes on for awhile, please bump this thread again in a few weeks. I've wanted to dig into machaut before, but it takes a good amount of time to come up with arguments for each note, ficta or not ficta.

The Machaut presents many issues for score study, and not all scholars (or practitioners) will agree with the ficta choices made by one editor or another. Ficta are, of course, suggestions which are usually there for any of several reasons (leading tone, avoidance of tritone, avoidance of flatted 7th in a major key 7th chord, to match accidentals appearing on the same degree in other parts, formulaic, etc. - including "because it sounds right").

Note (to Salieri): Schrade probably follows the accepted editorial practice that any accidentals which do not appear above the notes are accidentals that appear in the source. This seems to be especially so, given that frequently, say, a ficta C# is provided because of a non-ficta C# that occurs in a different part.

Anyway ... Here is my take on the questions raised by the O.P.:

- all flat accidentals on B (descending line from B), mostly appearing in the first part. most ensembles sing B flat, but Hilliard for example sings B natural. why did Schrade (and most others) insert them in the edition? aesthetically I have no preferation… any suggestions?

I have no strong preference, either, but I suspect that those who opt for the ficta B-flats do so on idiomatic grounds that may or may not have been idiomatic in Machaut's time. The B-flats begin a descending sequence of notes an occur at the highest point in their respective music phrases, which to some suggests flattening the top note. I haven't heard the Hilliard, but rather think the avoidance of these ficta B-flats may represent more recent scholarly thinking on the matter, which fits my own move towards more judicious use of ficta.

- bars 27, 101, 127, 129 : Schrade suggests an accidental on the F (becoming F sharp) - why? no recording I've heard so far features F sharp at that point… the only F sharp is at the beginning of the Amen part at bar 112.

Bar 27: The ficta F# in the Triplum does seem somewhat enigmatic, except possibly to "resolve" what would become a leading tone into the G on the resulting diminished chord formed by the four parts.

Bar 101: The ficta F# in the Triplum is probably there for two purposes, (1) to avoid a tritone with the Motetus, and (2) to avoid an augmented leap from F(natural) to the G# that follows in bar 102. Granted this ficta F# in the Triplum, it implies the corresponding ficta F# in the Contratenor in the same bar, which in turn implies the ficta C# in the Motetus (avoid a flatted 7th in a major 7th chord).

Bars 127, 129: the ficta G#-F# in bar 127 (into the G# in the next bar) is idiomatic and necessary to avoid the augmented second leap F to G# that would otherwise result; moreover, the ficta F#s in the Triplum in both bars and the ficta F#s in the Contratenor also have the effect of avoiding a D-minor chord resolving to a C#-minor chord in the ensuing bars, and hence they are probably also there to create a D-major chord resolving to C#-minor (which must have seemed more acceptable to Schrade).

on the other hand, Schrade doesn't suggest accidentals where they might be suitable as well. for example at bar 59 "peccata": the contratenor sings c-d-c(#)-d, but the first C on "pec-" could also be sung C sharp -> c#-d-c#-d. is this proper??

You cannot sharp the C on "pec" without creating a tritone with the G on "pec" in the Tenor part.

Fascinating!

to avoid tritoni

Thanks! You just triggered actual thought here, and now I know why Britten began the War Requiem WITH a tritone.

Thanks for the reminder, SNW. I have to say, it's a mess the more closely you look. I'd really like to see a facsimile of some early source. Bar 11, surely, is simply editor or engraver error: contrary motion to dissonance on the beat, parallel fifths, and parallel sevenths all in one bar.

In my opinion, further, most of the various sharps are wrong. Bar 4, the first, in Motetus voice is notated as if 'original' but I'd say it should be C natural, then the other sharps fall away. Here's my reasoning: begin with a D, call it 'tuned low'. (Doesn't matter, just a reference point). Bar 3 could be tuned in a variety of ways, but again doesn't matter because beginning of bar 4 is surely the same tuning as bar 1. Then, with the D tuned low, the A above it is tuned low and it goes with a C tuned high (a pure minor third). I'm inclined to think some of the manuscript marks that editors interpret as sharps are actually tuning indications: tune the C high, but don't make it a C#. So: bar 4, no sharps. Bar 7, same. I'd put a Bb in the Motetus, same as the following bars in Triplum. Bar 13, no sharps; bar 14, Bb. Bar 16, the sharp is ok. Bar 18, no sharps. That's as far as I've gone so far.