In 13th century music, the major 3rd actually comes across as a dissonance, and also to mention that music during that period was taught as a species of mathema

In 13th century music, the major 3rd actually comes across as a dissonance, and also to mention that music during that period was taught as a species of mathematics. Music theory is as easy (and as difficult) as trig. Learn the language. Learn the axioms. Understand the assumptions, please. And also understand that those assumptions can change at any time, depending on the musical period you're looking at!