In college, one of my favorite classes was music theory. I took piano lessons as a kid. I learned guitar as a teenager, and I knew the basics of chord structure, sight-reading music, harmony, etc.
However, I never knew the deeper reasons behind all of these things. I didn’t know why I liked to go from a five chord to the sixth minor chord. I never knew why the five chord likes to resolve to the one chord, and so on.
One of the things we learned in that theory class was the “proper” way to write a choral arrangement. We studied the great composers like Bach and how he would take a single melody and develop a four-part choral arrangement around it. What was so interesting is that all of the choral arrangements of this particular period followed a certain, fairly strict, set of rules.