When was music theory first studied?

Question

Music has been around for a long time, but how about music theory? What was the first instance of a publication on music theory?

Answer 1

In Western music the first could be said to be the 9th Century "Music Enchiriadis". Certainly there were writings on music before this (Boethius, Aristotle, Plato) but "music theory" in the sense you intend is probably this. See the Wikipedia article. A somewhat later treatise was called "Are Nova" --- "The term was first used in two musical treatises, titled Ars novae musicae (New Technique of Music) (c. 1320) by Johannes de Muris, and a collection of writings (c. 1322) attributed to Philippe de Vitry often simply called "Ars nova" today"