I tried mashing buttons to follow the intended usage as described on the game page. The engine ran out of sprites, resulting in an error screen. Specifically, it says "output_sprites vector is full. can't hold more sprites." Specifically that seems to happen whenever mashing buttons while holding the 7th chord button.
On the concept itself, I think this might be down to differing musical tastes or different expectations on who would use such a device. However, I think the idea of giving musical inspiration and the idea of restricting to only what will basically sound good are conflicting ideas. I've seen it elsewhere too, though, so your tastes might be more popular in the hobbyist game dev sphere. (also my liking of the locrian mode and modes in general may be an indication of what sort of musician I am)