Following the piezo Rochelle salts production, I’ve made a set of contact microphones. Those objects have been used by NSDOS.
The first thing to do was to find a way to connect 2 wires to the crystal.
Afterward, I’ve discovered that it can be done simply by heating the wires, which then go through the crystal. When the heating stops, the crystal hardens again, trapping the wires in it!
The first listening device was stereophonic and looked like pliers, allowing to listen to two faces of the same object.
The other listening objects were monophonic.
The main problem is the background noise and the sensitivity to interferences. It still lacks a good pre-amplifier to increase the sonic quality.