Thanks for sharing. I’m a musician and programmer, so I’m squarely in what I’d expect is your target audience. Since you’re posting an early version for feedback, here are some of my broadest initial thoughts.

From your README’s philosophy section: “You describe what you want to feel — ÆTHRA handles how it sounds.” But the rest of the documentation doesn’t yet feel aligned to that vision. The closest you get to that is when you describe your example chord progression as melancholic, but you as the composer already happened to know that this particular progression provides the feeling you have in mind.

I love the idea of a high level way to programmatically or idiomatically describe how music should feel, especially how the composition should evolve over time (perhaps even in surprising ways that are beyond current tools). I hope as you progress that you’re able to find innovative ways to build toward that vision.

The current feature set feels like it would be considerably more convenient in a GUI environment. Again, I hope that as you continue to build, it becomes more obvious why this is a language and not a visual synthesis/composition tool.

A little audio output demo would go a very long way in potentially getting me interested in playing around with this.

Good luck!