Analog synthesizer
An
analog synthesizer is a
synthesizer that uses
analog computer techniques and
analog circuits to generate sound electronically.
A very common circuit component in analog synthesizers is the
operational amplifier (aka op-amp). Many analog synthesizers contain many of them. Another common component is a
potentiometer (aka pot, or variable resistor), which is used to adjust the traits of the sound that is produced.
Some common analog synthesizer circuit components that consist of multiple parts are
low-pass filters and
high-pass filters.
Early analog synthesizers used technology derived from electronic analog computers and laboratory test equipment. They were generally "modular" synthesizers, consisting of a number of independent electronic modules connected by patch cables.
Synthesizer modules found in early analog synthesizers included:
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voltage-controlled oscillators
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voltage-controlled filters
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voltage-controlled amplifiers
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envelope generators
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low-frequency oscillators
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ring modulators
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reverb units
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sequencers
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sound mixers
Because many of these modules took input sound signals and processed them, an analog synthesizer could be used both as a sound-generating and sound-processing system.
Famous
modular synthesizer manufacturers included
Buchla & Associates,
Moog Music,
ARP Instruments, Inc., and
Electronic Music Studios.
Moog established de-facto standards for analog synthesizer control interfacing, using a logarithmic 1-volt-per-octave pitch control and a separate pulse triggering signal. These control signals were routed using the same types of connectors and cables that were used for routing the synthesized sound signals.
A very specialized form of analog synthesizer was the analog
vocoder, based on equipment developed for speech synthesis. Vocoders could be used to make a sound that resembled a musical instrument talking or singing.
Later analog synthesizers used the same building blocks, but integrated them in a single unit, eliminating the patch cords in favour of an integrated signal routing system. The most popular of these was the
Minimoog.
Famous makers of all-in-one analog synthesizers included Moog, Arp,
Korg and
Yamaha. Because of the complexity of generating even a single note using analog synthesis, most synthesizers remained
monophonic.
A second generation of analog synthesizers emerged later, with limited polyphony, typically supporting four voices.
Oberheim was a notable manufacturer of analog polyphonic synthesizers.
The
Polymoog was an attempt to create a truly polyphonic analog synthesizer, with sound generation circuitry for every key on the keyboard. However, its architecture resembled an
electronic organ more than a traditional analog synthesizer, and the Polymoog was not widely imitated.
In
1978, the first
microprocessor-controlled analog synthesizers were created by
Sequential Circuits. These used microprocessors for system control and control voltage generation, including envelope generation, but the main sound generating path remained analog. The
MIDI interface standard was developed for these systems. This generation of synthesizers often featured six or eight voice polyphony. With the falling cost of microprocessors, this architecture became the standard architecture for high-end analog synthesizers.
Analog synthesizers were mostly replaced by
digital synthesizers and
samplers over the late 1980s and early
1990s. In the late 1990s, a fashion emerged for "retro" analog synthesizers, with their proponents claiming that the "analog sound" of old analog synthesizers could not be accurately replicated using samplers or digital synthesizers. This led to increased demand for used analogs (such as the
Roland TR-808 drum machine and
Roland TB-303 bass synthesizer), the construction of a new generation of analog synthesizers (including modern-day modular synthesizers), and the development of a wide variety of
analog modeling synthesizers, which emulate analog
VCOs and
VCFs using samples, software or specialized digital circuitry.
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ARP synthesizer patents*
Modular Analog Synthesizers Return! - a discussion of modern modular equipment with links to major manufacturers.
