How do you make sound visible? That question occupied many researchers at the beginning of the 19th century. One of them was the English scientist Charles Wheatstone. In 1825 he developed this ‘Kaleidophoon’ or phonic kaleidoscope. This simple instrument consists of a beech wood board holding a number of thin metal rods with small balls at the ends. When a rod is slapped, it starts vibrating. The pace of the vibrations depends, among other things, from the thickness of the metal. This version, made by Rudolph Koenig, consists of several rods, the frequencies of which are tuned to one another. When the vibrating system is lit by a ray of light, the vibrations can be studied from the pattern of the patch of light.