Blog: Wavetable And Vector Synthesis Primer

Adam McLellan writes      09/10/13

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?

PPG Wave 2.3

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.

Waldorf MicrowaveIn 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:

http://www.waldorf-music.info/en/archive/ppg-wave-2v.html

If you're looking for something a bit more modern or versatile, check out Native Instrument's Massive:

http://www.native-instruments.com/en/products/komplete/synths-samplers/massive/

On that note, Quadrophone has put together a great resource: animations for all of Massive's wavetables!

http://quadrophone.com/massive-wavetable-images/

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):

 




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5 Comments...  Post a comment    original story
raphus    Said...

Sequential never made a wavetable synth. The Prophet VS used static digital waveforms, but four of them were dynamically mixed at a time. The effect could be reminiscent of a wavetable, but it was different. (With a little work and planning, Prophet VS-type mixing could be acheived on any ROMpler with four oscillators per voice.) Despite the article's title, it did not go into vector synthesis.

Some of the confusion also comes from the fact that some companies (DSI, Clavia, Creative) use the word "wavetable" to mean "digital waveform." Most people would agree that a true wavetable is a list of many distinct waveforms. Wavetable synthesis involves dynamically scanning through that list in a variety of ways. Otherwise, according to the DSI/Clavia definition, every synth with digital waveforms (Novation X-Station, Access Virus B, Roland JV90, all Korg VAs) would be a wavetable synth, and this is clearly not correct.

09-Oct-13 10:24 AM


Snug    Said...

Noted about the Prophet VS. I will make that correction.

I also agree about the grey area between wavetables and digital waveform cross-fading, and this article was meant to give some clarity to that.

I do touch a bit on Vector Synthesis on page 2 (including Roland and Yamaha's offerings), but the article is not intended to be an exhaustive resource on these types of synthesis. Again, I'm just trying to offer some clarity to up-and-coming synthesists.

Thanks for reading, and for the feedback!

09-Oct-13 12:22 PM


   Said...

RCM on the SY77/99 is NOTHING like LA synthesis - RCM is about incorporating PCM into an FM algorithm as a modulator or carrier. This is a whole different level of synthesis to LA synths which were just some sample playback alongside an early VA engine.

10-Oct-13 01:39 PM


madmax    Said...

Thanks for posting this. I read it yesterday. Coincidentally enough, on Wed, I visited a pawn shop where they had a Yamaha SY22 for sale for $49.95. I would have bought it but:

1. The (3rd party) power supply was taped to it, so I couldn't easily test it out.

2. More importantly, one of the keys was broken in that it wasn't flush with the others, and at least 2 other keys had some breakage underneath.

11-Oct-13 12:22 PM


brian from usa    Said...

Nowadays thanks to revisionist history I am starting to see the non-PCM portion of Roland's LA described as "virtual analog". It is certainly not VA in the sense we use today (digital models of analog circuits) although it is a subtractive engine with a "time variant filter". Even 1989 ears wouldn't have thought of the D50's filter sweeps as sounding analog!

21-Jan-14 03:57 PM


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