The "Licht-Ton Orgel" (Light-Tone organ) (1936)
A detail of the Light Tone Organ's glass disk.
The Welte Light-Tone, designed by E. Welte in Germany, 1936, was an electronic instrument using electro-optically controlled tone generators. A glass disk was printed with 18 different waveforms giving 3 different timbres for all the octave registers of each single note. The glass tone wheel rotated over a series of photoelectric cells, filtering a light beam that contolled the sound timbre and pitch.