The idea was to have a keyboard with silent keys. Result is quite opposite: each key has its individual sound pitch, making it easy to spy on what you type.
Electronic scheme consists of six 74hc165 shift registers with parallel input. Each key is connected to the individual input and pull-up resistor. Solid surface under the keys is connected to common wire. Two more 74hc595 are there to give 16 outputs to status LEDs (well, just one LED by now).
Keys themselves are a bronze wire with paper key cap glued together with hot-melted glue.
If you are going to build your own keyboard, try to avoid disadvantages of this design.
I forgot to mention. It was atmega128 project. I want not to disclose the firmware, because it is buggy and deprecated. I'll better write a new one.