Mr. Cohab gave me a note on which he had written the address to a website generously sharing a book on musical theory, explaining the methods of composition in a way that makes perfect sense (to my dense brain): Harmony.org.uk
So far, I’m actually on board with all the things dealt with in the book. Admittedly, I’m only just starting on Chapter 3, but all the same. I might just come out of this with a basic grasp of musical theory. Neato!