Digital Sound & Music: Concepts, Applications, & Science, Chapter 6, last updated 6/25/2013
subtractive synthesizer and then move on to a FM synthesizer. Once you’ve run out of sounds
you can create using those two synthesis methods, you’ll be ready to start experimenting with
some of these other synthesis methods.
Synthesizer Components 6.1.8
Now let’s take a closer look at synthesizers. In this section, we’re referring to synthesizers in the
strict sense of the word those that can be programmed to create sounds dynamically, as
opposed to using recorded samples of real instruments. Synthesizer programming entails
selecting an initial patch or waveform, filtering it, amplifying it, applying envelopes, applying
low frequency oscillators to shape the amplitude or frequency changes, and so forth, as we’ll
describe below.
There are many different forms of sound synthesis, but they all use the same basic tools
to generate the sounds. The difference is how the tools are used and connected together. In most
cases, the software synthesizer comes with a large library of pre-built patches that configure the
synthesizer to make various sounds. In your own work, you’ll probably use the presets as a
starting point and modify the patches to your liking. Once you learn to master the tools, you can
start building your own patches from scratch to create any sound you can imagine.
Sound Generator
The first object in the audio path of any synthesizer is the sound generator. Regardless of the
synthesis method being used, you have to start by creating some sort of sound that is then shaped
into the specific sound you’re looking for. In most cases, the sound generator is made up of one
or more oscillators that create simple sounds like sine, sawtooth, triangle, and square waves. The
sound generator might also consist of a noise generator that plays pink noise or white noise. You
might also see a wavetable oscillator that can play a pre-recorded complex shape. If your
synthesizer has multiple sound generators, there is also some sort of mixer that merges all the
sounds together. Depending on the synthesis method being used, you may also have an option to
decide how the sounds are combined (i.e. through addition, multiplication, modulation, etc.).
Because synthesizers are most commonly used as musical instruments, there typically is a
control on the oscillator that adjusts the frequency of the sound that is generated. This frequency
can usually be changed remotely over time but typically, you choose some sort of starting point
and any pitch changes are applied relative to the starting frequency.
Figure 6.20 shows an example of a sound generator. In this case we have two oscillators
and a noise generator. For the oscillators you can select the type of waveform to be generated.
Instead of your being allowed to control the pitch of the oscillator in actual frequency values, the
default frequency is defined by the note A (according to the manual). You get to choose which
octave you want the A to start in and can further tune up or down from there in semitones and
An option included in a number of synthesizer components is keyboard tracking, which
allows you to control how a parameter is set or a feature is applied depending on which key on
the keyboard is pressed. The keyboard tracking (Kbd. Track) button in our example sound
generator defines whether you want the oscillator’s frequency to change relative to the MIDI
note number coming in from the MIDI controller. If this button is off, the synthesizer plays the
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