Resonance Apparatus Simple Form

Comprising a hollow wooden resonance box, with two meter rules graduated in millimetres, mounted on top on either side along the length.

One each of brass and steel wires of different diameter attached to fixed bridge on one end of the box and tensioned by wrest pins at the other end.
A pulley mounted at the end supports third wire over it with masses suspended to the wire end. Includes two short and two long bridges for adjusting length of vibrating strings, and additional wires one each of steel and brass of 22SWG.