The terpodium is a friction instrument with a keyboard.
Terpodion of the Viandrina Museum in Frankfurt a.d. Oder
A wooden rod is rotated by using the mechanism of a sawing machine. When pressing a key a hammer is pressed against the rotating rod and a mechanism similar to bowing a violin string happens.
The sounds have a large variety of possibilities, from a regular sound to subharmonics, bifurcations, hammerings or noise.
Below is a Power Point presentation with sounds from the instrument investigated at the Viadrina museum in Frankfurt a.d. Oder:
More videos can be found here: