The A section starts off in the key of C major and uses only major chords and one dominant 7 chord. But I wander to as many different keys as I wish, temporarily. I wrote this etude to show that it is possible to write something creative with only major and minor chords.
I want to use this major tonality in this section to express something that is very peaceful and rather stately.
The rest of the story:
I am repeating the A section with the same idea but now moving to E major instead of C major. I’m modulating using the “trinity of major chords” idea.
For the B section I go back to the key of C, but this time I chose C minor, a modal change. I use this section for development, and now I’m using only minor chords.
I complete the section in the key of G# minor.
I want the B section to totally contrast with the A section. This should be serious, dramatic, moody and darker.
Now I am repeating the A section again but with only half as many measures to make the repeat of the A section seem like the right length dramatically. I am again using the idea of the “trinity of major chords” again. So I move from G# minor to a flat major, which is really the same key so far as what we hear and see in our hands.
This allows me to complete the “trinity of major chords” by moving from Ab major right back to C major and leaves me in the same key in which I started. Now all I have to do is add an ending cadence and I am done.