If the terms "wavetable", "wave sequence" and "vector synthesis" sound alien to you then you've come to the right place; in this month's post I'm going to explore the subtle differences between these types of synthesis and offer some hardware and software options for getting started.
What is a wavetable?
Wavetable synthesis was introduced by PPG in the 1970s and can be found on their line of Wave synths. Simply put, a wavetable is a collection of single-cycle waveforms. Typically these single-cycle wavesforms evolve or morph in some way as they progress through the wavetable, for example, by adding or removing harmonics, or changing formants (more on that later.)
In traditional analog synthesis one voice would comprise one static single-cycle wave (i.e. saw, pulse, wave). Wavetable synthesis, on the other hand, allows the programmer to select a base index (position) from the wavetable and then modulate this position relative to the selected index. As you can imagine, stacking and modulating these waves can produce complex evolving sounds, unlike anything that can be done with traditional subtractive synthesis.
To use an analogy, think of the human vowel sounds: a, e, i, o u. If this were represented as a crude wavetable it would consist of 5 single-cycle waves (in reality you'd probably have many more, but for the sake of simplicity let's say 5).
Now let's say the initial wavetable position is "i", and the position is being modulated by an LFO at 100% intensity. The end result would be something like: i-o-u-o-i-e-a-etc. Now, take this sound source and run it through the conventional architecture of a subtractive synth--pitch modulation, amplitude envelope, resonant filter, etc.--and you have the basis of a wavetable synthesizer.
In addition to the PPG Wave and Waldorf Microwave synths, wavetable synthesis can be found as a synthesis mode on some synths produced by Ensoniq, Korg, Access and Dave Smith Instruments. If software is more your thing, Waldorf offers a VST version of the PPG Wave 2:
Here's an example of two wavetables being swept by an LFO and cross-faded by another LFO. I gradually fade in a static addictive waveform, whitenoise and a ring modulator for extra texture (Access Virus TI Snow):