IC9 has a dc around -2 to 2.5v that rises to about -0.5 then drops to around -4v then returns to around -2.5v. (as a pattern) I took some photos..... Hitting keys does not seem to influence this pattern
Ic39 (the one above ic31) does not have anything happening on pin3. IC31 has -10v on pin3.
I was about to replace ic31 but thought I would hold off as ic9 doesn't seem to be doing what you described.
Will try again with the photos!
Thanks again