Blog: Wavetable And Vector Synthesis Primer

Adam McLellan writes      09/10/13

Differences with wave sequences

While wave sequencing can produce similar results to wavetables, the underlying architecture is actually quite different. Firstly, rather than using single-cycle waveforms, it's based on looped PCM samples--in some cases this includes multi-cycle waveforms with separate attack transients. Secondly, the sequence is entirely user-definable: rather than using modulation to cycle sequentially through waveforms one can define arbitrary steps, with each step having its own duration, level, and cross-fade time. (To use an another analogy, think of a DJ cross-fading one track into another into another etc. etc. )

Image Wikipedia

As with wavetable synthesis one can typically route this complex "oscillator" through traditional subtractive synth architecture.

Wave sequencing was introduced by Korg's Wavestation and has since made its way into their OASYS and Kronos synths. It can also be found on Arturia's Origin. If you're looking for a software option, Korg has released a VST version of the Wavestation as part of their Legacy collection: http://www.korg.com/LegacyWAVESTATION

Here's an example of a "motion pad" consisting of 3 separate wave sequences (Korg Wavestation):

Vector synthesis
In some ways vector synthesis is very much the same as wave sequencing: the ability to cross-fade between multiple sound sources (usually 4). Typically this is done with a joystick but in some cases it can also be done with an LFO or envelope.

Image Wikipedia

Korg's Wavestation implementation of "Vector Synthesis" is even more elaborate, however: each "vector" is a tone generated using a wave sequencer, each with its own envelope generators, LFOs, filters, etc.

Vector synthesis was first introduced by Sequential Circuits' Prophet VS in the 80s, and subsequently appears on Yamaha' SY series, Korg's Wavestation and OASYS, and Arturia's Origin.


Linear Arithmetic Synthesis (LAS) and Realtime Convolution and Modulation Synthesis (RCM) 
Roland D-50

Linear Arithmetic Synthesis was introduced by Roland's D-50 and D-550 synths in the late 80s. It can be viewed as a combination of virtual-analog synthesis and PCM wave sequencing. A sound consists of three parts: a PCM-based attack transient, a single-cycle PCM "body", and a traditional virtual analog synth waveform (saw or pulse).

(I have to give a shout-out to the talented producer ASC who cites the D-50 as one of his favourite synths: http://theasc.blogspot.ca/2013/07/gear-talk-1-asc-and-his-roland-d-50.html )

Along the same lines, Yamaha's SY77/TG77 and SY99 allowed for the playback of PCM-based "attack transient" waveforms alongside FM synthesized sounds. They called this "Realtime Convolution and Modulation Synthesis", but it essentially boiled down to the Yamaha/FM equivalent of Roland's LAS.

Where to go from here?
Why should you bother with this type of synthesis, you ask? Well for one thing, there's a limit to what can be done with traditional analog or virtual analog synthesis. While subtle variations in oscillators and filters can create some sonic variation, the base architectures between analog synths are typically quite similar. FM synthesis, on the other hand, can often be difficult to tame and tends to get into "metallic" and "bell-like" territory far too easily. 

Wavetable, wave sequence, and vector synthesis sit somewhere in the middle: a nice melding of digital and analog principles. 

If you're looking for a starting point I would recommend NI's Massive VST for wavetable synthesis, and Korg's Wavestation VST for wave sequencing and vector synthesis. While the latter has a much steeper learning curve it can be used to synthesize some very complex sounds, such as the one heard above. The downside of the Wavesatation is that the UI can be at times awkward and unintuitive, and it only offers two types of filters (-24 dB/octave resonant low-pass, exciter)

Adam McLellan, AKA Snug, is a DJ and producer based in Halifax, Nova Scotia, Canada. Since a young age he's been fascinated by the intersection of art and technology. When he's not producing or performing he's sharing his knowledge and ideas through teaching, writing for his personal blog (snugsound.com)




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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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