Comprising a wooden resonance box with two rules 1 meter long. Brass and steel wire of different diameter attached to fixed bridge and tensioned by fine adjustment pegs, two moveable bridges, pulley and fixed screw to enable a third wire to be fixed for tensioning by masses. Comprising a wooden resonance box of 114 cm length, 12.5 cm width and 10 cm height, with two rules 1 meter long sub-divided into millimeters. One each brass and steel wire of different diameter attached to fixed bridge and tensioned by fine adjustment pegs, two moveable bridges, pulley and fixed screw to enable a third wire to be fixed for tensioning by masses. One each additional wire of steel and brass, each 1.5 m long and of 22 SWG.
