ALESIS ANDROMEDA A6 - Manual (Page 84)

Chapter 3: Basics of Analog Synthesis
82 A NDROMEDA A6 R EFERENCE M ANUAL
For both pitched and non-pitched sounds, there are two key
elements of sound that we will be working with when
creating or editing Programs on the A6. First, we need to
consider what makes up a sound wave: what are the
components of a sound wave and how do they relate to the
A6? Second, we need to know that sound changes over a
period of time, which can be a mere fraction of a second to
several minutes (or longer). Let’s take a few moments to
cover these two elements.
A L
ITTLE
T
HEORY
W AVEFORMS
All audible sound consists of waveforms or waveshapes. These
are the vibrating air waves our ears perceive as sound, and
can be described by their “form” (or the “shape” of the
wave) when depicted by a graph. Waveforms can be
illustrated by simple graphs that show how they would
appear on the display screen of an oscilloscope, an electronic
device used to analyze sound waves. The graphs in the left
column illustrate what the basic waveforms look like.
Waveforms are the primary components of the “raw” sound
in a synthesizer. But instead of a “vibrating object”, these
waveforms are generated electronically. This is the function
of an analog synthesizer that we mentioned just a moment
ago: the electronic approximation of sound waves that occur
in nature.
The A6 uses 32 oscillators – electronic circuits that produce
raw waveforms – to simulate naturally occurring sound
waves. For our purposes in operating the A6, we’ll classify
waveforms into two types based on their shape:
• Cyclical or periodic waves repeat a particular pattern over
and over. The main property of a periodic wave is that it
has a musical pitch or tone. Periodic waves, therefore,
are especially useful when attempting to synthesize
traditional instruments such as violins and other stringed
instruments, brass and horns, reed instruments and so
forth. By the same token, periodic waveforms are useful
when synthesizing entirely new sounds that don’t sound
anything like a violin or a clarinet.
The A6 provides four periodic waveforms which are
described by the shape of the sound wave they create:
Sine, Triangle, Pulse and Sawtooth. These four basic
waveforms have distinct sound personalities and lend
themselves to producing certain kinds of sounds as we
will discover later.
• Non-cyclical or aperiodic waves are irregular and do not
have any particular pattern that is repeated. The main
property of an non-cyclical wave is that it does not have a
musical tone. Aperiodic waves, therefore, are especially
useful when synthesizing wind, thunder, explosions or