I have been asked whether Marc-Antoine Charpentier changed his
handwriting during some re-workings of this manuscript, and whether he
also changed his clefs in these re-workings.
The answer is, No, that is someone else's hand.
On the pages below, this other hand did in effect add comments or examples to Charpentier's autograph treatise. In the images below, these additions are surrounded with red lines. (Images courtesy Lilly Library, Indiana University, Bloomington, Indiana)
The individual who inserted these additions appears to have been the unidentified author of the Traité d'accompagnement. I say "appears," because although the hand that drew the musical examples on folios 3 verso and 6 verso is undeniably the same hand that did the musical examples in the Traité, the handwriting in the statements added to manuscript "XLI" sometimes resembles quite closely the script in the Traité, but sometimes it disintegrates into a hen-scratch sort of shorthand (as in the emendations on folios 4 verso and 5 recto).
folio 1 verso:
folio 3 verso:
folio 4 verso:
folio 5 recto:
folio 6 verso: