I am writing an instrumental orchestration of De Machaut's Messe de Nostre Dame, Kyrie. I found scores in IMSLP here and here.

These scores show accidentals above notes, sometimes in parenthesis. I am not sure how to treat those. Listening to performances, it seems that some are used and some are not, notably, the ones in parenthesis aren't while the ones without sound like "regular" accidentals before the note.

I believe that the harmony is hexachordal, however, any analysis I try to make in order to explain which accidentals should appear where fails at some point (can provide details if needed).

What are the rules for the accidental placements and their performance?

Also, in the first link, the score has "bridges" over groups of notes which I understood to be modernized ligatures. How should those be treated? (I can ask a separate question on this if requested.)

Edit: apparently Wikipedia has the answer.

  • 1
    "Listening to performances, it seems that some are used and some are not" - there are differences of opinion between scholars, and also performers who take the exact contents the original manuscript copy as the equivalent of holy writ, which it never was. Also, tastes have changed over time. If you compare a modern-notation edition made in the 19th century with a recent one, you will probably find the 19th-century version was converted into something closer to major and minor scales and common practice harmony than what current scholarship would consider to be "informed performance practice".
    – user19146
    Oct 15, 2015 at 21:19
  • 1
    The brackets are transcribing ligatures in the original notation. For your orchestration, you can safely ignore them. For the accidentals, though, it would be best to get the most recent edition you can find from a library and then trust the editor and use the "editorial accidentals" above the staff. If it is a good edition, then the editor is a musicologist who knows more about medieval musica ficta than can be found on Wikipedia. Oct 16, 2015 at 22:15

2 Answers 2


They all mean the same thing and tell you to play the note notated no matter the case, but why they are there is different for each.

  • When it is to the left of note as normal, it is just a typical accidental that the composer wrote in.

  • When it is to the left of note as normal, but is also in a parenthesis, then it is a courtesy accidental. This kind of accidental is to remind you this accidental is applied to the note, but is not needed and is more for reminder purposes.

  • When it is above the note, it is an editor's suggestion. It was not in the original score, but it may make more sense than what the original score contained. You can play either what's written with, or without, the accidental above the note.

  • In practice, if I choose to apply one of the optional accidentals, do I need to apply others too? Oct 15, 2015 at 16:30
  • @user1803551 You would typically want to with playing them or ignoring them. If you mix them then you may not get the desired affect you want which is either a very true to the original piece or a more modern sound.
    – Dom
    Oct 15, 2015 at 16:41
  • This answer completely misses the point that early music had "ficta" where the performer was supposed to infer the accidentals. In modern editions the editor will often supply them, since performers don't usually have that skill themselves. Jun 26, 2022 at 21:37

That is a modern transcription of musica ficta.

Musica ficta entry at Wikipedia

Musica ficta entry at Brittanica.com

The original music did not usually contain accidentals within the music. Musicians were expected to fill them in as needed. Most of the in-music accidentals (except possibly for B and B flat) are likely editorial additions. The ones without parentheses are those that the publisher considers mandatory (or that did, after all, have some indication in the source), the others are merely possible but do not reflect the publisher's opinion.

The modern listener tends to find versions with most of the accidental suggestions more natural but that's partly due to modern ears being more accustomed to major/minor tonality than modal tonality.


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