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Vochrome Vochrome (detail) David Tudor, Bandoneon! (a combine)
Tool Identification

Name of tool: Vochrome
Creation date: 1966
Designer: Robert Kieronski

Historical Notice

Robert Kieronski developed the Vochrome in the mid 1960s, while Bell Labs was refining the Vocoder, invented by Homer Dudley in 1939. The Vocoder analyzed and synthesized speech, originally with the objective of reducing telephone voice bandwidth. The Vochrome belongs to the family of sound analysis instruments, which includes the human voice (1). Unlike the Vocoder, it did not synthesize sound. One of the applications targeted by Robert Kieronski was musical accompaniment of the human voice in real time. David Tudor put the instrument’s initial functions to new use in Bandoneon! (a combine). He rerouted the bandoneon’s audio signal, captured by the microphones, to the Vochrome in order to control the lights and sound: “Bob Kieronski, a friend of mine, designed a device which he called the 'Vochrome'. It was a set of harmonium reeds, pirated from a harmonium, in an enclosure that was made to be as soundproof as possible, because my desire was not to have the sound of the reeds present. And I attached two contact microphones inside the bandoneon to vibrate the reeds. Bob designed the Vochrome so that it would mechanically vibrate relays, and then he recalled that he had in his basement some old relays and that he could connect them to the Vochrome. One day, when we were trying it out, he said that the only problem with the relays was that they're in sequence and you have to start a sequence from the beginning, so would you like it if I put a switch on your bandoneon so that you can reset the relays to zero. That was one of the most important things, because by touching that button I could stop the sound. The silence was deafening, because the sound in the Armory was extraordinary, so reverberant. Once you started something oscillating, it would go on forever.” (2) 

Tool Description

“The Vochrome is an original design for an electro-mechanical spectrum analyzer. It separates audio frequencies and harmonics into channels corresponding to notes on the tempered scale of music.” (3) 

Summary of Materials

Wooden box containing an electromechanical component module.


American harmonium reeds, electronic circuitry, transistors.

Operating Procedure

“The input to the Vochrome was an audio signal (such as from a microphone). There were 48 discrete digital outputs (0/1), each corresponding to a note on the tempered scale. Singing, for instance, an "A" 440hz would activate the "A" output. The device was crude, but it worked!

Physically, it consisted of an acoustic chamber that was "pumped" by an array of loudspeakers. The audio was coupled to a bank of brass reeds from a reed organ (each reed being a high Q resonator at its own frequency). Sympathetic vibration was induced in the reeds and sensed and integrated by simple transistor circuits. The output could then be used to drive (for instance) a pipe organ to play what you were singing into the microphone.

The "chrome" part of Vochrome came from the fact that no attempt was made to suppress resonances or intermodulation products. So, if the Vochrome was fed a complex waveform, several outputs could go high at once. These would be "related" to the input in some physically derived but somewhat chaotic fashion. Hence, the device would add its own "color" to the process. (4)


Control of musical instruments or electric relays via an audio input.

Documents Consulted

Robert Kieronski, The Vochrome. Published on the Internet at:

Robert Kieronski, email addressed to Clarisse Bardiot, July 16, 2005.

Joël Chadabe “A conversation with David Tudor,” (1993). Published on the Internet at:

Robert Kieronski, Vochrome – Vochromator (for David Tudor). Experiments in Art and Technology. Records, 1966-1993, Research Library, The Getty Research Institute, Los Angeles, California (940003).

Vincent Bonin © 2006 FDL

(1) In this regard, see Bruno Bossis, La Voix et la machine : la vocalité artificielle dans la musique contemporaine (Rennes: Presses universitaires de Rennes, 2005).

(2) David Tudor, quoted in Joel Chadabe, “A Conversation with David Tudor,” 1993. Available on the Internet at:

(3) Robert Kieronski, The Vochrome :

(4) Robert Kieronski, in a email to Clarisse Bardiot, July 16, 2005.