I suppose the missing features are the voice-leading lines as in the last chord of the first Kyrie? That should work with the \glissando feature.

I would be happy to have these put up at the github! There are two or three spots where, to make the coding easier, they differ from the NOH, but the spots all have to do with the time values of accompaniment notes, and wouldn't affect the harmonies when it is played.

Protasius - yes, the voice leading lines need to be added, as well as a few brackets indicating which hand plays certain notes. Those things exist in Lilypond, I just was in a hurry to get it done for this past weekend.

Jpal - this template is a bit cluttered, but the 1/2 time signature with the bar lines invisible has the benefit of grouping the neumes slightly better than if you use \cadenzaOn the whole time. I'm not sure this is the best way to write stemless, accompanied chant, but it seemed the best way to transcribe the NOH.

Thanks to cantorconvert's excellent template, I was able to transcribe Credo I and Credo III. See the attached PDFs, or build them with Lilypond yourself from the code.

I changed a few things code-wise to experiment with Lilypond NOH transcription:

• Mark the entire score with cadenzaOn so that I don't have to turn on and off bar lines.
• Use note durations (sixteenth notes) to reflect the tightened horizontal spacing for neumes. (This depends upon SpacingSpanner.packed-spacing being off, which gregorian.ly turns on by default).
• Put voice-leading lines in their own voice, and draw them as glissandi.
• Use StaffGroup instead of ChoirStaff so that double bar lines extend between staffs.

A transcription of Mass IX is attached. Source codes are available at CMAA GitHub.