Photograms are a primitive, camera-less form of photography. Light-sensitive, silver gelatin paper is placed underneath an object and exposed to light. The variation of shadow and light create the resulting image.
Water Cymatigrams are an elaboration of this concept, utilizing water and sound frequencies. By projecting sound frequencies into a shallow tray of water, these vibrations are visualized in unique standing wave patterns. Photo-sensitive paper is then placed into the vibrating water, and the image is made.