I designed a relative piano-roll-based music notation. I used 12 colored arranged in a specific way to make visible the main effects and oppositions of Western tonal harmony. The tonic is always white, so a manual annotation/interpretation is required for each MIDI file.

All chords are flags of three to four colors. Minor mode is darker, major mode is lighter. Colors are arranged in thirds.

I sorted the pieces from simple complex harmony. I also wrote a bit of text to explain what you may see. There's also a corpus of structures: hyperlinks of tags that allow you to find similar patterns throughout my corpus of 3000+ popular pieces.

My method makes chord progressions memorizable and instantly visible in the scores. No preparation of Roman numeral analysis / chord symbols analysis is required. After a bit of training the chords will stare right in your eyes.

It's not synesthesia, it's a missing script for tonal music which makes harmonically identical things look the same (or similar).

I've also recorded lectures on my method in Russian (https://www.youtube.com/playlist?list=PLzQrZe3EemP5pVPYMwBJG...). I'm sorry I haven't yet found time to re-record in English.

I've also sketched a friendlier intro: https://vpavlenko.github.io/d/

Sorry, but this thing won't make any sense if you're color-blind.

It's open-source: https://github.com/vpavlenko/rawl

Earlier context: https://news.ycombinator.com/item?id=39165596

(Back then colors were less logical, and there was no corpus of 3000+ piece annotated yet)