I am fascinated by piano chord progressions. Quite apart from the musical element, I find the science and art of the whole thing to be quite entrancing. I find it a superb mental exercise working out the progressions – the more complex, the better. I like the mathematical elements – counting up, counting down, the skips, and the steps. I also like the poetic side of it – there is a rhythm to all this. And I like the logical beauty – the patterns that hold their own, even when keys are transposed.
The music is great, but these other things add their magic. It is a rich, fulfilling hobby on its own, even far away from an actual piano. In this sense, the sounds of the piano come as confirmation, a sweet reward for all the mental effort. I like that too.