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Table Of Contents
Appendix B Synthesizer Basics 501
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
rst 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 rst instrument to do so. This
synthesizer had two digital oscillators, combined with analog lters and amplier circuits.
The Synclavier, introduced in 1976 by New England Digital Corporation (NED), was the rst
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 aord.
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). Peaveys DPM-3, released in 1990, was the rst 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-denable samples.
Another solution was to design synthesizers as a computer peripheral, rather than as a
standalone unit. The growing popularity of personal computers from the early 1980s made
this option commercially viable. Passport Soundchaser and the Syntauri alphaSyntauri were
the rst examples of this concept. Both systems consisted of a processor card with a standard
musical keyboard attached to it. The processor card was inserted into an Apple II computer. The
synthesizers were programmed via the Apple keyboard and monitor. They were polyphonic and
had programmable waveforms, envelopes, and sequencers. Today’s sound cards, introduced in
countless numbers since 1989, follow this concept.
Exploiting the ever-increasing processing power of today’s computers, the next evolutionary
step for the synthesizer was the software synthesizer, which runs as an application on a host
computer.
The sound card (or built-in audio hardware) is needed these days only for audio input and
output. The actual process of sound generation, eects processing, recording, and sequencing is
performed by your computers CPU—using the Logic Pro software and instrument collection.