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Appendix B Synthesizer Basics 476
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Hybrid analog and digital synthesizers: Some synthesizer designs feature digital oscillators
that generate signals—using binary descriptions of waveforms. The digital oscillator signal is
then sent to analog lters and ampliers. The main advantage of this approach is that digital
oscillators don’t drift in pitch, which is a common problem in analog oscillators.
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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, lters, and other modules that you would nd in an analog synthesizer are
emulated by computer algorithms.
ES1 is a virtual analog synthesizer. Its virtual signal ow is that of a typical analog synthesizer, but
all components and signal processing—the virtual oscillators, lters, and so on—are calculated
by the central processing unit (CPU) of your computer.
ES1 emulates some of the idiosyncrasies of particular analog circuits—in cases where they tend
to sound nice—such as high oscillator levels overdriving the lter. Other analog synthesizer
phenomena, such as slowly drifting out of tune (as the instrument heats up), are not simulated.
Virtual analog synthesizers have other advantages over their analog counterparts as well. They’re
programmable, which means that you can save sound settings; they can be automated, so you
can record and play back fader and knob movements; and they are often multitimbral, which
allows you to play dierent sounds at the same time, on dierent instrument channels. Aspects
such as polyphony—the ability to play multiple notes—and velocity sensitivity are found in
most virtual analog synthesizers but in very few analog instruments.