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In a synthesizer, the task of tone generation falls to a component known as an oscillator.
Most synthesizer oscillators generate harmonically rich waveforms, such as sawtooth,
triangle, square and pulse waves. These waves are named due to the resemblance of their
shapes to the teeth on the blades of a saw, to triangles, to squares, and so on. For
information about the most common synthesizer waveforms, see Oscillators.
Sculpting the fundamental tone and related harmonics into another sound is achieved
by routing the signal from one component, also known as a module, to another in the
synthesizer. Each module performs a different job that affects the source signal.
In a modular synthesizer, this routing is achieved by physically cabling modules to each
other. In most modern synthesizers, however, the signal routing between modules is
internally prewired and is typically changed using switches, knobs, and other controls.
For a discussion of the various synthesizer components and how they interact with each
other to control and shape your sound, see How Subtractive Synthesizers Work.
Synthesizers have been around for much longer than you may think. In the days that
preceded the use of digital technology, all electronic synthesizers were analog. And prior
to the use of electricity, synthesizers were actually mechanical. If you’re interested in
learning more, see A Brief History of the Synthesizer.
Analog
An analog synthesizer combines voltage-controlled circuits—such as oscillators, filters,
and amplifiers—to generate and shape sounds. The amount of voltage is typically related
directly to the waveform pitch, with higher voltages equalling higher pitches.
Digital
In a digital synthesizer, the signal flow is digital. Binary descriptions of the signal—a string
of zeros and ones—are fed from one algorithm to another.
Hybrid Analog and Digital Synthesizers
Some synthesizer designs feature digital oscillators—which generate signals that are sent
to analog filters—and amplifiers. The main advantage of this approach is that digital
oscillators don’t drift in pitch, a problem that analog oscillators are often notorious for.
Virtual Analog
A virtual analog synthesizer is a digital synthesizer that mimics the architecture, features,
and peculiarities of an analog synthesizer. The behaviors and functions of the oscillators,
filters, and other modules that you would find in an analog synthesizer are emulated by
computer algorithms.
The ES1 is a great example of a virtual analog synthesizer. Its virtual signal flow is that of
a typical analog synthesizer, but all the signal processing—the virtual oscillators and so
on—is performed by the central processing unit (CPU) of your computer.
352 Appendix Synthesizer Basics