This video demonstrates the principle of a Marloye’s harp.

The masses of four pendulums are backed to the inside of a glass vessel. When an arch rubs against the edge of the vessel, the vessel vibrates and emits a sound. The vibrations produce the pendulum motion. A lanyard is attached to the end of a rectangular wood plate fixed to a support. Some powdered resin is spread on the foil. Under the action of a bow, the string vibrates and transmits the vibrations to the foil. The complex vibration modes, which depend on the direction and the movements of the bow, are shown by the figures produced by the powder. Marloye’s harp consists of a heavy pedestal on which are fixed vertically twenty fir rods. Rosin powder is spread on the fingers to increase their friction on the temples. These produce different notes when they are rubbed between thumb and forefinger. The sounds are generated by longitudinal vibrations. The lengths of the rods are such as to reproduce a color scale.