Exidiophone, An Electro-Acoustic Instrument
Exidiophone is an audio-feedback (Larsen Effect) based musical instrument which does not have any oscillators or audio sources.
An audio-feedback is a phenomenon that produces a constant tone by repeating an amplification of a sound from a speaker to a microphone.
The figure above explains a basic structure of Exidiophone. An usual audio feedback keeps amplifying until a capability of its amplifier circuit. On the other hand, Exidiophone has a light sensor which controls amplifier’s volume and a LED which is placed on the other side of light sensor. The LED is turned off when the gain of a signal coming from the microphone exceeds a threshold. Thus it works as:
- A loudness of audio-feedback increases
- LED is turned off
- Light sensor makes the volume lower
- Audio feedback stops
- LED gets back to on
- back to 1
Then Exidiophone outputs feedback sound with periodical feedback-tone and silent along with the on and off of the light, self-regulatorily. The speed of period can be controlled by changing capacitors which is placed on a socket on a body of exidiophone.
Document
Idiophone, one of the category of musical instruments, has an origin in the meaning that “The object itself makes a sound” like cymbals and Marrimba, not like a Membrenophone like drums or Chordophone like piano and guitar.
Thinking about Speaker literally, it means “a someone who speaks”. It is made for producing a loud voice instead of a human or reproducing auditory information by speaking recorded voices instead of people.
A word Microphone comes from micro and phone. It picks up and amplifies small sound having an origin in the role of Sthethoscope.
Even if the speakers and microphone can record all the sound which exists on earth until now, we can still find a blank area that is not filled with “found sounds” and can be produced with a speaker and a microphone.
Such a sound is “The sound which Speaker and Microphone themselves produces”.“Ex"idiophone expands the notion of “The sound which the object itself produces” on Idiophone and also expands a view to existing electronic musical instruments.
Photos
2018年4月、《Alternative Act 1.0 Tech Performance Fes.》でのパフォーマンスの様子。当日は2台持ち込んだが1台がオペアンプの故障で音が出なくなり、1台+スピーカー2発でのパフォーマンスとなった。2日間のパフォーマンスだったが、2日目にはもう1台からも本番直前で音が出なくなってしまったので急遽別のパフォーマンスをすることになった。
