My Chant Glossary at Corpus Christi Watershed was published March 12, 2023, and last updated August 30, 2023.  Although I conceived of it as a collaborative page that could be edited by myself, Ostrowski, Weaver, Frederes, or any other contributor, it turned out to be a solo project.  As I no longer contribute to that site nor have editorial privileges, any updates must be made here.  In the entry for Kainzbauer, I would have done better to write of digitization rather than digitalization.  Here are two additional entries:

absonia (pl. absoniae) – literally discordance or harshness; used to describe tritones and other melodic dissonances

free rhythm – this term may be used in several senses: 1. lack of meter (regular pattern of stressed and unstressed beats); 2. recitative or cantillation, in which note values are only approximate; 3. music without a tactus, beat, or pulse; or, improperly, 4. rubato.  In sense 1, we may certainly speak of free proportional rhythm, as lack of meter neither necessitates nor implies flexible or approximate note values.  In sense 2, the rhythm of the text takes precedence over the musical notation.  Sense 3 would more accurately be called arrhythm, but such is the usage of all amensural or antimensural schools of chant: accentualist, Solesmes, and semiological, although the Solesmes method admits a pulse that is constantly in flux by being stretched out, sped up, or slowed down, which is considered qualitative rather than quantitative, resulting in a nuanced interpretation that can still be counted, but without a truly steady pulse.  Sense 4 renders the notation subservient to every interpretive whim, to the extent that the performer is “free” to do whatever he wants with it.