Our current system (staff, clef) isn’t even that old. The system used before that one is still understood, in order to ‘translate’ early music into modern notation. Good thing too.
Rediscovering Awe: Antoine Brumel’s “Earthquake Mass”
https://europeanconservative.com/articles/essay/rediscovering-awe-antoine-brumels-earthquake-mass/
I just listened to that hymn from the video linked in your post. Awe-inspiring - thank you.
https://www.youtube.com/watch?v=3QIEA02J8Ms