In 1855 the French researcher Jules Antoine Lissajous (1822-1880) developed a method to make sound vibrations visible by means of light. He did this by making a light ray reflect subsequently on two perpendicular, vibrating mirrors. If such mirrors vibrate in certain harmonic proportions, a so-called ‘Lissajous' figure’ is formed on the projection plane. In 1874 S.C. Tisley and his partner Spiller devised a method to record these figures graphically. In their ‘Harmonograph’ a pencil is coupled to both vibrating mirrors. Depending of the times of oscillation and the starting moments of the oscillation (the phase) different figures of Lissajous are formed. Figures in lamp-black can be projected onto a screen.