I wonder how much the chord-space would shrink farther if you took out the bridge/intro where people tend to mix it up. And if you could adjust when the song shifts keys in the chorus and verse. (Although I didn't keep up with all the simplifications so maybe that is already in here).
> Although I didn't keep up with all the simplifications so maybe that is already in here
That one isn't there, because the original motivation of the post was trying to design a chord input system for an instrument. In which case I'm happy telling the instrument in advance "this next song is in Dm" but not changing that on the fly (hands are full)
