I guess this is a very early model from Johannus, 70ies? It includes 4 divider tone generators, over 100 tabs, 12 speakers on the roof. All wooden keys are hand crafted with long levers – a wonderful physical experience.
BUT: its sound is totally unsuitable and jarring. Only the reed tabs sound quite nice, and some chiff effect to some pipes, but I did not understand, how this was made. It is impossible to find a circuit diagram for it, and the wiring inside is confusing and rather chaotic. After I repaired most obvious things, I decided that I will not want to listen to this sound any more, and decided to rebuilt it to a digital MIDI console for GrandOrgue and Hauptwerk (modern pipe organ programs for PCs).
One Arduino Mega was sufficient to do the scanning of all keys, pedals and tabs with a scanning frequency of 70 Hz, this has no notable latency.