The “Brain” is a Atmel ATMega32 microcontroller.
Lower board with voltage regulator µC and later the MIDI connector.
The upper board is for the display and some switches.
Short introduction of the Midi- Keyboard Controller
Here the 2. part of the MIDI- keyboardcontroller which shows the whole Setup on the workbench.
Here is the 3. part where i try to explain how to create the control voltages in a polyphonic Synthesizer.
Here is the 4. part of the series. I show a very simple implementation of a polyphonic synthesizer.