Jyotiophon  (optical theremin)

This is an instrument I brought with me from a time travel to the year 2034. ;-)  This name jyotiophon (or "jiotiofono" in Esperanto, the common language of time travellers) derives from "jyoti", the sanskrit word for "light", because light is the medium this instrument employs to recognize the player's body movements to translate them into ethereal sounds. The jyotiophon is played similar like a theremin/ aetherophone (see here), but unlike the latter it works without the emission of nervous system maladjusting radio waves, because it locates the hand positions solely by light beams from integrates lamps - reflected by the player's body at the light sensors.

The instrument can make a lot of bizarre, howling tones; some resemble a singing saw, some resemble a motor bike, others can resemble a Hawaii guitar and many sound like distorted C64 SID sounds. Also subsonic, fat and knocking basses, synth- toms and even bell- like metallic clangs can be played with some skill.
The instrument has 4 ludcirkloj ("play circles") those each consist of a light bulb and a corresponding light sensor to determine the hand position.
  • left back = pitch,
  • right back = volume
  • left front = efekto frequency
  • right front = efekto intensity
From left to right you see the knob for frequency ludcirklo sensitivity, 2 knobs and a switch to control the sensitivity and frequency of the built-in efekto unit (ring modulator(?)/ distortion) and the main volume knob. Above these is the power switch button.

main features:

Here is a close look at the analogue electronics...
...here you see the frequency ludcirklo with attached deflector mirror...
...and here the cardboard bottom of the case.


This instrument reacts very allergic on artificial light from mains operated lamps or CRT based TV sets or such monitors, because the 50 Hz light flicker modulates the pitch frequency of the main oscillator (which makes it buzz like EM radiation from a badly shielded electric motor disturbing radio reception or a motorcycle sound simulated in a historical tv-game). Thus the instrument works only well in a dark room or with dim daylight.

The other problem is that the light reflected by the hand must not interfere the sensors of other ludcirkloj, thus I had to mount the light sensors into small dark plastic tubes to make them react only when hands are directly above them. The frequency ludcirklo responds badly non- linear which makes it severely difficult to hold the pitch, because it reacts often way too sensitive when the hands miss the center of the narrow light beam. The wacky, attachable deflection mirror also doesn't make the situation really better, but just changes the left hand movement from vertical to horizontal, which is slightly less strenuous. I guess the optics would need to be reworked much to function well.

The efekto unit (ring modulator?) was made from a "robot voice" electronic voice changer kit and the case has been made from a modified Curver makeup tray.

not to forget: If anybody will ask you what a jyotiophon or a theremin is, just reply:
"It's a flyolin - neither a flute, nor a violin - a flyolin!". ;-)
 removal of these screws voids warranty...    
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