Just out of idle curiosity. I went to music school and teach at a local music shop, so I’m very familiar with music theory but I’m aware that my experience is most likely not the norm.
If you are familiar with any theory (even just scales and keys), where did you pick it up? Lots of the resources I’ve seen both in and outside of formal education can be both confusing, and it’s often hard to see the application of what you learn in the short term.
As a computer musician: enough to construct a scale / mode and stay in it. Enough to construct chords. But I’ve never put the effort into learning notation because I don’t play an instrument (properly), and I’m grumpy about how much cruft there is in music theory. Like, the basic unit is the semitone, which should be called the whole tone. And the naming of intervals just pisses me off. “A fifth? Oh, that’s seven semitones.” Ugh. So I’ve never really advanced at chord theory.
I did take an intro to music theory class in college, but I every-good-boy-does-fine’d my way through it and it didn’t really stick. I got a lot out of “How Music Really Works” by Wayne Chase, though. No notation.