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It was not until 1978 that the problem was resolved. The five-voice polyphonic Prophet-5,
released by the American company Sequential Circuits, was the world’s first synthesizer
with a global storage feature. All settings for each of its five onboard monophonic
synthesizers were stored in memory slots—40 in the debut model. Moreover, all five
synthesizers shared a single user interface, which simplified matters considerably. In spite
of its initially high price, this instrument proved extremely popular and approximately 8,000
were built up until 1985. In addition to its digitally implemented polyphony and memory, the
success of the Prophet-5 is due to the quality of its analog sound generation system.
Digital synthesizers
Modern digital synthesizers featuring variable polyphony, memory, and completely digital
sound generation systems follow a semi-polyphonic approach. The number of voices that
these instruments are able to generate, however, no longer depends on the number of
built-in monophonic synthesizers. Rather, polyphony depends entirely on the performance
capability of the computers that power them.
The rapid developments in the digital world are best illustrated by the following example.
The first program that emulated sound generation entirely by means of a computer was
Music I, authored by the American programmer Max Mathew. Invented in 1957, it ran on a
university mainframe, an exorbitantly expensive IBM 704. Its sole claim to fame was that it
could compute a triangle wave, although doing it in real time was beyond its capabilities.
This lack of capacity for real-time performance is the reason why early digital technology
was used solely for control and storage purposes in commercial synthesizers. Digital
control circuitry debuted in 1971 in the form of the digital sequencer found in the Synthi
100 modular synthesizer—in all other respects an analog synthesizer—from the English
company EMS. Priced out of reach of all but the wealthiest musicians, the Synthi 100
sequencer featured a total of 256 events.
Ever-increasing processor performance made it possible to integrate digital technology
into parts of the sound generation engine itself. The monophonic Harmonic Synthesizer,
manufactured by Rocky Mountain Instruments (RMI), was the first instrument to do so. This
synthesizer had two digital oscillators, combined with analog filters and amplifier circuits.
The Synclavier, introduced in 1976 by New England Digital Corporation (NED), was the
first synthesizer with completely digital sound generation. Instruments like the Synclavier
were based on specialized processors that had to be developed by the manufacturers
themselves. This development cost made the Synclavier an investment that few could
afford.
An alternative solution was the use of general-purpose processors made by third-
party computer processor manufacturers. These processors, especially designed for
multiplication and accumulation operations—common in audio processing tasks—are
called digital signal processors (DSPs). Peavey’s DPM-3, released in 1990, was the first
commercially available synthesizer completely based on standard DSPs. The instrument
was 16-note polyphonic and based mainly on three Motorola 56001 DSPs. It featured an
integrated sequencer and sample-based subtractive synthesis, with factory presets and
user-definable samples.