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Sequential Prophet VS [Retrozone]

Vector Synthesizer
Published November 2001

Sequential Prophet VS

Boasting one of the most intuitive methods of sound creation ever devised, 1986's Prophet VS was meant to be US synth giant Sequential's commercial saviour. Sadly, it didn't succeed — but it did earn itself the status of American Classic...

The 1980s were a productive time for synthesis, with ever‑more complex methods of sound creation, using various combinations of analogue and digital technology, being developed. Yamaha had started the ball rolling in 1983 with digital FM (Frequency Modulation) synthesis, which came to prominence in the DX7. Frequency Modulation was followed in 1985 by Casio's PD (Phase Distortion) synthesis, as used by the CZ101 and CZ1000. In the same year, Korg decided to get in on the act, with DWGS (Digital Waveform Generator System), found on their DW6000 and DW8000 synthesizers. Then Roland came to the digital party in early 1986 with SAS (Structured Adaptive Synthesis), a method originally intended to produce that 'perfect piano sound' — in the infancy of sampling, still something that was keenly sought‑after. A year later, Roland followed up with their LA (Linear Arithmetic) synthesis, which first appeared on the famous D50.

If you're confused, don't worry — you're not alone. Most of these different synthesis methods ended up baffling musicians, programmers and hi‑tech salespeople alike. It's no coincidence that an entire industry based around software editors for synthesizers (mostly on the Atari and Amiga computers) grew up between 1985 and 1987.

It wasn't that musicians didn't want to create sounds from scratch any more — though, admittedly, factory presets had improved enormously during this time. It was simply that, in most cases, the synthesis structure within their instrument was so complex that they simply couldn't work out how to, or didn't have the necessary time to devote to learning. The new synthesis combinations seemed endless, but what did they all mean? And, more important, what did these scientific‑sounding methods actually do to the sounds that they generated? In fact, instead of making life easier, the new, complex synthesis methods ended up mystifying and irritating many players, who simply resorted to using factory preset voices.

Synth Wars

Such was the rather muddled state of the synth market in the summer of 1986. But at the same time that Yamaha, Roland and Korg were producing ever‑increasing numbers of the new synthesizers at reasonable prices, the American‑manufactured synth was becoming an endangered species. Products from giants such as Moog, ARP and Oberheim, that had once dominated the market, were now vanishing, as company after company went out of business.

Sequential were one of the US synth 'giants' who were having difficulties. Indeed, from being the top seller of electronic musical instruments in 1982 they had become yet another struggling American synth manufacturer trying to compete against a flood of cheaper Japanese competitors. They needed something big to restore their flagging fortunes, so the decision was made to re‑introduce the 'Prophet' name that had made the company so famous in the late '70s and early '80s, in the shape of the Prophet VS (Vector Synthesizer). The launch of the VS, however, meant the introduction of yet another new method of synthesis into a keyboard marketplace that was already apathetic, crowded and somewhat confused.

Perhaps predictably, keyboard players were in no mood to be won over that easily. They wanted to know what it was that made 'Vector Synthesis' special, and why it should make them invest in the new Prophet VS. The ones who dismissed the VS as just another complicated sound‑producing method that would only make their lives more difficult missed out on a real event. For Vector Synthesis was, and probably still is, in my opinion, the most incredible way ever conceived of creating sound. (Actually, Vector synthesis was not so much a new method of synthesizing sound, as an entirely new approach to structuring it.) Prior to physical modelling, which has only recently become available, I think it's probably the single most important sound‑generation development of the last decade or two. And it's testimony to this importance that a series of later musical instruments, such as the Korg Wavestation series and Yamaha's SY22 and SY35, incorporated Vector technology.

Vector Victor

The VS transmits all its Vector parameters over MIDI, and also allows very small user samples to be loaded in via MIDI Sample Dump — a facility that was years ahead of its time.The VS transmits all its Vector parameters over MIDI, and also allows very small user samples to be loaded in via MIDI Sample Dump — a facility that was years ahead of its time.

The Prophet VS is a 61‑note, five‑octave, 16‑note polyphonic, programmable synthesizer with a velocity‑sensitive keyboard and a MIDI specification that's especially good for a synth of this vintage. All the parameters of Vector synthesis are assigned, recognised and transmitted — a MIDI sophistication that befits a keyboard from a company that was so instrumental in the establishment of MIDI, and that made the first‑ever MIDI synth, 1982's Prophet 600. There's also a unique on‑board arpeggiator that allows 'overdub' arpeggiation and is thus capable of producing very sophisticated patterns. The VS has 100 factory sounds (stored in 10 banks), made up from multiples of waveforms that could be effected with a built‑in stereo chorus unit, and even panned in real time.

The 128 waveform possibilities that the VS offered consisted of 96 factory‑preset waves, plus a further 32 user‑definable waveshape locations. The real beauty of the synthesizer was that, for the first time, you could create totally new, previously unheard sounds almost instantly. It was as simple as choosing four waveforms, assigning them to the four oscillators (vector points), and then moving the VS's trademark joystick around freely until you heard something pleasing. Movements, or 'vectors' could then be saved, and the sound played back. It was even possible to apply the recorded vector path to another sound altogether and see what happened.

It all seems straightforward, and theoretically it is. The clever bit on the part of the synthesizer is calculating smooth transitions between the four oscillators and their associated waveforms as the user moves the joystick into positions between the four vector points. Though this form of synthesis had been known about in theory for some time, it was only the advent of sufficiently powerful digital processors that allowed it to become a reality. The sophisticated overlay algorithms determining the percentages of waveform characteristics that would be heard at any point still had to be calculated, of course. And it was this, the smooth transition between oscillator characteristics, that Dave Smith and his design team at Sequential were so pleased about when they finally got it to work.

Sequential Prophet VS

Film Star?

The result is a unique sonic experience. The Prophet VS really sounds like no other synthesizer of its time — and, I would venture, none since. Capable of emulating a Prophet 5, an Oberheim, a PPG or a Jupiter 8, the VS can also create sounds that are unmistakably DX7‑like, and still others that are completely unique to it. Some sounds caused such a sensation when the Prophet VS was first heard that they have become a part of synthesis folklore. Patch 69, 'Filmusic', is one such sound, a haunting combination of strings and pads that swirl from left to right and back, as the oscillators seem to vie for attention.

In the VS, Sequential practically single‑handedly pioneered the use of stereo and multi‑dimensional sound positioning for keyboard players, giving them a totally new way of expressing themselves. One indication of the popularity of the VS method and sounds is the sheer number of film soundtracks that were composed almost entirely using the Prophet VS. These often haunting, flowing textures are unmistakable, and they're still used to this day. Nine out of ten movie sound designers will own a Prophet VS — and treasure it.

We May Have A Problem...

The heart of Vector Synthesis, the four‑way Waveform Mix joystick.The heart of Vector Synthesis, the four‑way Waveform Mix joystick.

Of course, as great as the VS was, there were some drawbacks. Firstly, it's easy to break irreplaceable parts of the VS, such as the data slider or joystick assembly. Also, the velocity‑sensitive keyboard was a total disaster, with most not working when they were new, much less 15 years later. Indeed, the overall build quality of most of Sequential's products at this time was quite poor. Second‑hand buyers beware. There was a time when Dave Sesnak and his wonderful team at Wine Country Inc. in San José could supply all the bits needed for repairs, but spare parts for Sequential instruments, especially the Prophet VS, are now increasingly hard to get hold of.

Other VS drawbacks were more conceptual. Not the least of these was the theory of creating totally new sounds via the reality of a small, two‑line LCD display in which all the synthesis parameters needed to be shown. The problem is that, though its joystick interface is very immediate, the Prophet VS is not an easy instrument to learn. Programming a VS can be a real chore, and while it became a lot easier with the advent of third‑party programmer‑software packages, in most cases people simply didn't want to build their own sounds from scratch and were happier going out and buying somebody else's work on a ROM pack, or (later) a floppy disk.

The End Of Sequential

Despite its innovation, the Prophet VS came too late to rescue Sequential. The synth's chances of success in the UK were hampered by the fact that when it first appeared here the US Dollar was particularly strong. This meant that the instrument cost a whopping £1899 — very expensive when the DX7 was selling for just £1249. Sequential's financial position at the time also meant that they could not make and sell enough units for the VS to make a wider impact. Consequently, the VS is still a fairly rare instrument, with total production figures of around 2500 for the keyboard, and just 900 for the rack‑mountable version.

The VS also marked Sequential's last serious attempt to regain their lost status in the synthesizer market, as they concentrated their design efforts on samplers afterwards. However, despite the best efforts of the Prophet 2000, the Prophet 2002, and the later Prophet 3000 (another piece of pure design genius, and way ahead of its time), Sequential, with crippling financial problems, were finally bought out by Yamaha just over a year after the VS first appeared.

The main body of the VS development team was divided by Yamaha, but remained for some time under the direction of Dave Smith (the founder of Sequential Circuits, as Sequential were previously known). One half would eventually be responsible for the design and development of the Yamaha SY22 and SY35 vector synthesizers, both loosely based on the Prophet VS. The remainder of the team went to Korg, which had also been purchased by Yamaha at about the same time as Sequential. They went on to develop the Korg Wavestation series, evidently based on the Prophet VS, and quite possibly a classic synthesizer of tomorrow. In so doing, they solved some of the difficulties that had been associated with the programming of sounds on the Prophet VS by using 'wave tables' — though, as anybody who owns a Wavestation will tell you, it's still not a simple instrument to fully understand and learn. Vector synthesis is complicated stuff.

Is the Prophet VS the greatest digital synth of all time? In my opinion, sound‑wise, it comes close, and there are many who would agree with me. Certainly the VS has had a long life — its continual use by composers of film and television music place makes it one of very few instruments that has truly stood the test of time.

I think it's fair to say that to those who own a Prophet VS, it's as valuable a sound source today as it was when first released — even in the modern, sample‑dominated musical world.

The Price Of Prophet

If you want to buy a Prophet VS today, you'll have to look quite hard for one, as they don't appear that often. Usually they sell for between £800 and £1100, which is a good indication of how valued and sought‑after an instrument the VS is. The rack version is rarer still, selling for between £750 and as much as £1450.

More On Vector Synthesis

The Prophet VS is noted for producing sounds that have depth and dynamism, and is capable of considerable sonic complexity, but the synthesis system at its heart is simple enough to describe. Essentially, a collection of 96 waveforms — 12‑bit samples — is supplied, and though they're numbered rather than named, you'll recognise analogue standbys such as sine, sawtooth and pulse waves. The remaining waves include material suitable for purely imitative sound creation, and aggressively digital waveforms that you'll be unlikely to hear elsewhere. Four of these waveforms are assigned to the oscillator slots (labelled A, B, C and D) at the heart of a VS patch, and they are then processed by an essentially analogue signal path, with low‑pass filters based on the legendary Curtis four‑pole chips; similar devices were used in Sequential's classic Prophet 5. Curtis chips are also used for the VCA and Sample & Hold facilities. It's this combination of digital and analogue that helped make the synth's sound stand out from its mid‑'80s, purely digital, competition. And the VS's influence is still being felt, in the later digital synths mentioned in the main body of this article, and even in software: the Orpheus soft synth that forms part of Arturia's Storm software studio features a four‑way joystick interface and is clearly inspired by the VS.

Each of the VS's four oscillators, A‑D, can have a waveform and frequency value assigned to it (see Oscillator Group switches above). These waveforms are then accessible for real‑time combination via the joystick. Curtis chips form part of the synth's analogue filter architecture.Each of the VS's four oscillators, A‑D, can have a waveform and frequency value assigned to it (see Oscillator Group switches above). These waveforms are then accessible for real‑time combination via the joystick. Curtis chips form part of the synth's analogue filter architecture.

Three envelope generators are provided, one each for amplitude, filter and oscillator mix; these are unusual in being five‑stage, 12‑parameter devices, with the option to loop any stage, backwards or forwards, infinitely or a fixed number of times. The results can be rather like a user‑definable LFO, adding some real movement to a finished patch. There's a pair of proper LFOs, too. The last stage in the VS's signal path is a simple stereo chorus unit, perhaps the single most disappointing aspect, sonically, of the instrument.

The 'vector' in Vector Synthesis comes into play when the VS's joystick is manipulated. Its several tasks include providing real‑time control over oscillator mix, with the joystick at the centre of two axes, A‑C and B‑D. Wiggle the joystick to change the perceived level of the oscillators. During patch editing, the joystick can also be used to customise waveforms, as mentioned elsewhere in this article. You select a waveform for each oscillator slot, give it a frequency value (which multiplies a waveform's fundamental frequency), and tweak the joystick. Listen to the way the waveforms interact with each other — frequency values have an effect on this interaction — and when you hear something you like, store the result as a custom waveform. It's even possible to use custom waveforms as the basis for more custom waveforms, further increasing complexity and depth. Additional flexibility is offered by joystick control of each stage of the VS's mix envelope.

You're not restricted to internal waveforms, either: MIDI Sample Dump Standard was a new concept at the time of the VS's release, and the VS was one of the first synths, as opposed to samplers, that supported it. The available RAM for your own samples is hopelessly small by today's standards — I've seen it described as 128 words — but it should provide enough space to upload interesting attack waveforms (a lá Roland's LA synthesis of about the same period). The manual provides information on how to make the best of this limited facility. At least SDS's legendary sluggishness won't be an issue with so little RAM!

Quite aside from the joystick, modulation via the LFOs, velocity, aftertouch, pitch‑bend and mod wheel can be applied to virtually any VS parameter. Two finished patches can be layered or split, with two‑part multitimbrality.

There are 100 patch memories on board the VS, and a cartridge slot allowed users to access third‑party sounds via ROM carts, or save more of their own to RAM carts (a RAM cart can also store 32 user waveforms). Wine Country Sequential ( have RAM carts for sale, along with manuals, promotional literature, software upgrades and limited spares (before you ask, it looks as if replacement joysticks are unavailable). The OS revision of a VS can be checked during power up, when it scrolls in the display. Version 1.2 is the last update, but a VS with earlier software can be updated. Wine Country Sequential can provide a user‑installable two‑chip set (with full instructions) for US$34.95 plus shipping. The update usefully adds Local Keyboard On/Off and transpose modes, syncs the LFO to key presses, and offers an Increment/Decrement function that allows very small parameter changes to be made without the data slider. Derek Johnson

Published November 2001