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Table Of Contents
Appendix B Synthesizer Basics 477
Subtractive synthesizers
How subtractive synthesizers work
There are many approaches to sound creation with a synthesizer. (See Other synthesis methods
overview on page 491.) There are also numerous dierences between synthesizer models, but
most follow a fundamentally similar architecture and signal ow 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 lter, or cut away, 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.
Subtractive synthesis assumes that an acoustic instrument can be approximated with a simple
oscillator that can produce waveforms with dierent frequency spectrums. The signal is sent
from the oscillator to a lter that represents the frequency-dependent losses and resonances in
the body of the instrument. The ltered (or unltered) signal is shaped over time by the amplier
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, subtractive synthesizers aren’t perfect at emulating real-world instruments. No
synthesized clarinet is going to be mistaken for a real clarinet—particularly when compared to
samplers like the EXS24 mkII, which are able to recreate real instruments far more convincingly
by using multigigabyte sound libraries.
The true strength of subtractive synthesizers is that they oer a unique sound palette of
their own.