Perhaps you could do a hierarchical approach somehow, first generating a "zoomed out" structure, then copying parts of it into an otherwise unspecified picture

Perhaps you could do a hierarchical approach somehow, first generating a "zoomed out" structure, then copying parts of it into an otherwise unspecified picture to fill in the details. But perhaps plain stable diffusion wouldn't work - you might need different neural networks trained on each "zoom level" because the structure would vary: music generally isn't like fractals and doesn't have exact self-similarity.