It's done. After two month i finally could bring myself to close the lid.
Ok , it is done and it works the way it is intended. But is it any good? Short answer: Sound bad, haptic good.
The sound is not good. The only thing i goot out of it was a decent "spooky ghost noise". A rectangle with AM and FM is just not enough to make a good general purpose syntheziser. It is just too simple. After never finishing some way too complex attampts, i over did it in the other direction.
However, the mechanical keyboard itself is quiet nice. If you look at effort vs result, it is phenomenal. It is also very cheap and easy to make and it is very playable. Just some Tact-switches on a pcb and a 3D printed part. It can be used analog (as i did) or just read out digital.
So my final recomendation is: If you need a simple cheap keyboard for your project, copy what i made. If you need a nice syntheziser look somewhere else. But it was still fun to put it together. Note! This is just for the device. The subcircuits work fine.