Having a lifetime of visual art background, it was just natural for me to try to imagine and draw as I study music. I would recommend everyone to also learn to read sheet music, I think these visuals for instruments really help and they complement sheet music notation - they are for different things.
These drawings show the pull of harmonies, the tensions built by harmonies as if it was height. As the key center changes, the direction of the gravity changes in the drawings.
An inspiration was a concept shared by John Abercrombie that functional improvisation is like Playing a straight line through a circle, and modal improvisation is like Playing a circle around a straight line.
Blue bossa
Solar
Solar compared to So what. See how the thread in Solar tries to be the minimum/shortest path, while in so what, it builds up the imaginary harmonies for us.
Drop 2 chords are very popular basic 7th diatonic chords on the guitar, they help to free up people from open string chords and barre chords, really fun. The shapes below helped me memorize them, they feel a little like strings in a cat's cradle game, as I image them being pulled into space by my finger. Maybe they help you too! Here is a PDF version.
Various drawings of scales below. If not clear, these are moslty drawings of the guitar neck, with 1st position to the left, often 5th, 7th, 12th are marked.
The minor pentatonic scale. The red one is what most people start with. Now that I learned all the inversions, my favorite is the yellow one.
Drop 2 7th chords over the pentatonic scale, some clean some spicy.
Triads. The foundation. And how they flow into each other.
Tetrachord fun
Read more here:
https://en.wikipedia.org/wiki/Tetrachord
One specific example where I found them very useful was to try to remember/make sense of Mozart / Don Giovanni Overture scale runs:
2 note per string scales
2-5-1 chord tones overlaid on minor and major scales
The modes of C
These sheets combine the melody, chords, some scales and chord tones for improvisation over the song. Of course there are many ways to play over these, and I might have made mistakes even, but I had fun using these ideas to study these songs.