of Microprocessors

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Voltage Control Methods
As briefly mentioned in Chapter 1, the development and use of voltagecontrolled
sound synthesizers was an important milestone in the history of
electronic music synthesis. More than any other single development, it
served to popularize synthesis methods not only with the listening public but
also with composers and performers.
Voltage control is really a fundamental concept. For the first time there
has been established a one-to-one correspondence between an easily manipulated
physical variable, a voltage level, and each of the important parameters
of sound. Thus, manipulation ofa voltage would actually be manipulation of
a frequency, amplitude, formant position, waveform distortion parameter,
etc. Frequently, voltage-controlled techniques are characterized as continuous
or analog techniques because one physical variable (the signal or control
voltage) represents another physical variable (amplitude, frequency, etc.).
Also of importance is the modularity of voltage-controlled synthesizers.
The synthesizer itself is nothing more than a package for holding a number of
independent modules that may be interconnected in literally an infinite variety
of ways. The number of simultaneous sounds and their complexity is dependent
mainly on the type and number of modules available and the means
available for controlling them. Only a very few modules are required co
produce single simple electronic sounds. More are required for implementation
"Of subtle variations and multipart harmony. If a given complement of
modules is insufficient for a particular application, more are easily added at
moderate cost.
Compatibility is another key characteristic of voltage-controlled synthesizers.
All inputs are compatible with all outputs, meaning thac any physically
possible permutation of interconnections is also electrically safe and
potentially useful. Furthermore, in some instances outputs are compatible
with each other. In such cases, two outputs plugged into the same input
(with a "Y" connector, for example) actually results in mixing of the two
signals involved in equal proportions. Compatibility often extends to the
point that different manufacturers' modules may be easily interconnected.
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