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Appendix B Synthesizer Basics 494
Wavetable, Vector, and Linear Arithmetic synthesis
Wavetable synthesis uses a number of dierent single-cycle waveforms, laid out in what is known
as a wavetable.
Playing a note on the keyboard triggers a predetermined sequence of waves. In general, this is
not a stepped transition but rather a smooth blend from one waveform into another, resulting
in a constantly evolving waveform. Multiple wavetables can also be used simultaneously—
either played one after the other, or blended together—resulting in more harmonically
complex waveforms.
A single wavetable can emulate lter cuto with a series of bright, less bright, then dull-sounding
waveforms played in sequence—which resembles a reduction of the lter cuto frequency in a
subtractive synthesizer.
Wavetable synthesis isn’t well-suited for emulating acoustic instruments. It is noted for producing
constantly evolving sounds; harsh and metallic, or bell-like sounds; punchy basses; and other
digital tones.
Wavetable synthesis was championed by the PPG and Waldorf instruments. The ES2 and Retro
Synth also include wavetable features.
Roland LA (Linear Arithmetic) synthesizers such as the D-50 work on a similar principle. In these
synthesizers complex sampled attack phases are combined with simple sustain or decay phases
to create a sound. In essence, this is a simple wavetable that consists of two samples.
Where LA and wavetable synthesizers dier is that the latter were designed to create new,
original, digital sounds. LA synthesizer designers, in contrast, wanted to emulate real instruments
using a minimum of memory. To achieve this goal, they combined samples of the attack phase—
the crucial part of a sound—with appropriate decay and sustain phases.
Vector synthesis—used in the Sequential Circuits Prophet-VS and Korg’s Wavestation—allows
you to move through wavetables and sequences arranged on a two-dimensional grid (two
dierent vectors, or less technically, on the X or Y axis). The main benet of this approach is
that the balance between samples and waves is achieved in real time by moving a joystick. You
can also use the ES2 to perform vector synthesis by modulating the Oscillator Mix (Triangle)
parameter with the Vector Envelope.