I generally avoid these kind of threads, but I like the way you are seeing and defining 'music theory'. I have two music degrees and, in doing such a thing, I've studied a great deal of music theory and use it quite a bit in playing bass, composing and arranging. However.... I have performed and continue to perform in several groups in which many of the members would claim then "don't know much (or any) music theory". Some don't read music.
I enjoy very much watching and listening to these so-called uneducated musicians and I'm often very impressed with the way they've constructed their own 'music theory'. Many of them could not really articulate how the elements of music work, yet they understand them very, very well in their own way. They know what notes work best together, what chords are needed for different styles. Often times their power of observation is keener than musicians who have studied a broad scope of music. They memorize quickly and hear very well. And.. most important, they understand how sounds and rhythm work together.
The upshot of all this is.... I don't believe them when they say they 'don't know music theory'. They do. They just don't know what Walter Piston has to say, or could do Hanson or Schenker analysis. So what? I guess the means they won't be teaching in a university soon. But... they are able to deal with the music they have at hand, and they DO know music theory.
Just thought this post deserved another reprint.
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Even drummers and singers need to know rudiments of pulse, meter, and form to play with other people)