This is really good stuff, and once again, I will risk sounding arrogant as I say that the Circle of 5ths is Music 101 and everybody who plays should know it, and have learned it before learned to play an instrument, or at the very least concurrently. This is why I tick everybody off when I tell them to learn MUSIC before they learn SONGS.

Start with whole whole half whole whole whole half (the steps in a major scale) and the 4th, the 5th,, the 7th... all of that explains itself. That formula works no matter what key you start on, and it is the cinder block foundation upon which a music house is built.

That Circle of 5ths chart has been around forever. I learned that at 4yrs 10 months of age, and my teacher would not allow me to touch a piano (I DID have a molded plastic keyboard mock up) until I knew that stuff COLD. That and when he pointed to a note on a scale I had to point to the corresponding key.

And 59 years later, I still say "Learn music. THEN learn songs."