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The ES1 includes some of the desirable idiosyncrasies of particular analog circuits—in
cases where they tend to sound nice, such as high oscillator levels overdriving the filter.
And undesirable analog synthesizer phenomena, such as the habit of going completely
out of tune, are not simulated.
Virtual analog synthesizers have a few other advantages over their analog
counterparts:they’re completely programmable (you can save sound settings), they can
be completely automated (you can record and play back fader and knob movements),
and they are often multi-timbral (you can play different sounds at the same time, on
different 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.
How Subtractive Synthesizers Work
There are a number of approaches to sound creation with a synthesizer (see Other
Synthesis Methods). Although there are numerous differences between synthesizer
models, most follow a fundamentally similar architecture and signal flow that is based
on subtractive synthesis principles.
According to legend, when Michelangelo was asked how he managed to carve David
out of a block of stone, he replied, “I just cut away everything that doesn’t look like David.”
In essence, this is how subtractive synthesis works:You filter (cut away) the parts of the
sound that you don’t want to hear. In other words, you subtract parts of the frequency
spectrum, consisting of the fundamental tone and associated harmonics.
The subtractive approach to synthesis assumes that an acoustic instrument can be
approximated with a simple oscillator—which produces waveforms with different
frequency spectrums. The signal is sent from the oscillator to a filter that represents the
frequency-dependent losses and resonances in the body of the instrument. The filtered
(or unfiltered) signal is shaped over time by the amplifier section of the synthesizer.
The distinctive timbre, intonation, and volume characteristics of a real instrument can
theoretically be recreated by combining these components in a way that resembles the
natural behavior of the instrument you are trying to emulate.
In reality, however, because subtractive synthesizers aren’t ideal for emulating real world
instruments, no synthesized clarinet is going to fool anyone—particularly now that there
are multigigabyte sound libraries available for samplers like the EXS24 mkII.
The real strength of subtractive synthesizers is that they offer a unique sound palette of
their own.
All analog and virtual analog synthesizers use subtractive synthesis to generate sound.
353Appendix Synthesizer Basics