Audio Synthesizer

[warthman@garnet.berkeley.edu]

********************** News Release ************************

November 5, 1992


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Neural-Network Audio Synthesizer Debuts at Paris Opera House
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Palo Alto, California -- The old Opera House in Paris, France, 
will feature five performances by the Merce Cunningham Dance 
Company, November 12 to 17, in which a new type of audio 
synthesizer based on an artificial neural network will be 
used to generate electronic music. The synthesizer's musical 
accompaniment was composed and will be performed by David 
Tudor and his dance company colleague, Takehisa Kosugi. 

The audio synthesizer is built around an integrated-circuit 
chip from Intel Corporation in Santa Clara, California. The 
chip, called the Intel 80170NX electrically trainable analog 
neural network (ETANN), simulates the function of nerve 
cells in a biological brain. 

A remarkable range of audio effects can be generated with 
the electronic synthesizer -- from unique space-age and 
science-fiction sounds to passages that sound very much like 
birds, heart beats, porpoises, engines, and acoustical, 
percussion or string musical instruments. Sounds are 
generated internally by the synthesizer. External inputs 
such as voice, music, or random sounds can optionally be 
used to enrich or control the internally generated sounds. 
In addition to generating outputs to multiple audio 
speakers, the synthesizer can simultaneously drive 
oscilloscopes or other visual devices. 

The neural network chip's software consists of numeric 
values representing interconnection strengths between inputs 
and outputs -- a configuration analogous to the excitatory 
or inhibitory strengths of synapse connections between 
biological nerve cells. The artificial neurons can be 
connected in loops, using the programmable interconnection 
strengths, or they can be connected outside the chip with 
cables and feedback circuits. Audio oscillations occur as a 
result of delay in the feedback paths and thermal noise in 
the neural network chip. The sounds are generally rich 
because of the complexity of the circuitry. 

The concept for the synthesizer evolved from a project begun 
in 1989 by Forrest Warthman and David Tudor. The synthesizer 
was designed and built by Warthman; Mark Thorson, a hardware 
designer and associate editor of Microprocessor Report; and 
Mark Holler, Intel's program manager for neural network 
products. 

John Cage visited the design group in Palo Alto a 
few months before his passing away at the age of 79 this 
year. His observations on the synthesizer's role in musical 
composition and dance performance contributed to its current 
design. 

A description of the synthesizer's architecture and 
circuitry will appear in the February 1993 issue of Dr. 
Dobb's Journal.