Okay, this site was the most interesting thing I'd found.
<https://silpayamanant.wordpress.com/music-notation-software/>"This is a growing list of music notation programs and resources which aren’t specifically Common Western Notations (CWN) programs."
There is a list of Byzantine Chant projects. If any are still active, perhaps their people might be able to help.
-- Karlin High Missouri, USA
