The Lumigraph hid a thin sheet of colored light just behind a stretched rubber screen in a dark frame; whatever touched the screen from behind, fingers, palms, tools, bloomed into glowing shapes. A performer played it like an instrument, silent itself, usually with music.
Fischinger built it around 1950 and performed it in Los Angeles and San Francisco; the device earned a patent, appeared decades later in a science fiction film, and survives in museum collections and reconstructions.
Among light instruments it stands out for being genuinely gestural: not keys triggering fixtures but hands sculpting light directly, closer to theremin than organ, and a clear ancestor of touch-driven visual performance.