Hello,

Assuming I could made a nice rochelle salt crystal like the one shown
he http://seawhy.com/xlrs.html, any suggestions on how to proceed
to make a piezo earpiece?

Some possible thoughts:
a. Spring clamp copper plates to 2 opposing surfaces and test with a
multimeter for piezo effect, then super glue a malleus to the top
plate and touch it to a foil drum. The plates are the electrodes.
b. Make a foil 'setting' for a small crystal, and touch the crystal to
a foil drum. The 'setting' and the drum are the electrodes.
c. Load several small crystals into a shallow can and insert a copper
plate with malleus [which touches a foil drum. The can and plate are
the electrodes.

Joseph