Digital Sound & Music: Concepts, Applications, & Science, Chapter 6, last updated 6/25/2013
somewhere in all those harmonics. All you need to do is subtract the harmonics you don’t want,
and you’ll expose the properties of the sound you're trying to synthesize. The actual subtraction
is done using a filter. Further shaping of the sound is accomplished by modifying the filter
parameters over time using envelopes or low frequency oscillators. If you can learn all the
components of a subtractive synthesize,r you're well on your way to understanding the other
synthesis methods because they all use similar components.
The opposite of subtractive synthesis is additive synthesis. This method involves
building the sound you're looking for using multiple sine waves. The theory here is that all
sounds are made of individual sine waves that come together to make a complex tone. While you
can theoretically create any sound you want using additive synthesis, this is a very cumbersome
method of synthesis and is not commonly used.
Another common synthesis method is called frequency modulation (FM) synthesis.
This method of synthesis works by using two oscillators with one oscillator modulating the
signal from the other. These two oscillators are called the modulator and the carrier. Some
really interesting sounds can be created with this synthesis method that would be difficult to
achieve with subtractive synthesis. The Yamaha DX7 synthesizer is probably the most popular
FM synthesizer and also holds the title of the first commercially available digital synthesizer.
Figure 6.20 shows an example of an FM synthesizer from Logic Pro.
Figure 6.20 A FM synthesizer from Logic Pro
Wavetable synthesis is a synthesis method where several different single-cycle
waveforms are strung together in what’s called a wavetable. When you play a note on the
keyboard, you're triggering a predetermined sequence of waves that transition smoothly between
each other. This synthesis method is not very good at mimicking acoustic instruments, but it's
very good at creating artificial sounds that are constantly in motion.
Other synthesis methods include granular synthesis, physical modeling synthesis, and
phase distortion synthesis. If you’re just starting out with synthesizers, begin with a simple