That delicious moment when you cleared all this occluding plastic and you start to grasp how everything works/worked ... especially when you have removed a hundred of screws .Too bad I didn't took many relevant photos.
Keyboard 2 - Vanilla
Observe the spring mechanism, the 121 diodes and the green pcb of the µC that we will happily remove.
A 8052 variant. Notice that the decoupling capacitors are faaar away from its Vcc pin : Lack of knowledge , space constraints or evil built-in obsolescence ? Even weirder, power is fed trough a 10ohms resistor to make a strange RC filter ... am I missing something of this is a broken design ?!
Yellowish Keyboard 1 - Modded
The previous DIY alternative that uses an Atmega8 and two shift registers to scan the keys. Every generated event is sent to a serial port, acquired by the pc through a serial<>usb converter and whatever serial<>midi software.
The 2 switches per key. The last C key (right) will be removed.
So absurdly long.