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The Sequential Circuits Prophet
VS
The Prophet VS was
made by Sequential Circuits Inc. between 1986 and 1987.
It was a
milestone partly because it was one of the first 'sample and synthesis'
(S&S) type synthesizers.
Even today it would be called a true
digital-analog(ue) hybrid! Nowadays everyone wants to call a synth
"Analogue", whereas in the 1980s the word "Digital" was the cool term to
use. As with the Prophet-5, most controls were set up to input 'data' to a
microcomputer which had these functions:
1. To scan the keyboard
for inputs and to assign a voice to each note played. The computer is
needed to handle several simultaneous inputs from the keyboard and to
control several sets of voice controls independently according to the
programmed parameters in the 'patch', unlike a monosynth, which
essentially has one input (a simple voltage from the keyboard whose value
is defined by the key pressed - like a simple potentiometer) directly
controlling one voice.
2. To store the program settings. The VS had 100 patch programs in on-board memory,
plus an optional data cartridge which stored another 100 programs.
In
addition, the Prophet VS had digital oscillators which always stayed in
tune, unlike the fickle analogue oscillators of earlier Prophets, whose
pitches were liable to vary mostly with temperature, and even slip completely
out of tune, usually completely without warning! This was now not a
problem. The digital oscillators (4 per voice) had accurate tuning and
this could be adjusted for each of the 4 oscillators independently for a
given patch, to give the required level of detuning to fatten the sound
etc. In addition, it was possible to vary the detuning between the 8
voices when they were 'stacked' into one note in 'Unison' mode, which gave
quite a giant monosynth sound with basically 32 detuned oscillators
operating when you played a note.
Each digital oscillator could play back one of about 128 sampled waveforms. Each wave
was a single cycle sampled waveform, giving a wide choice of starting points for the sound,
giving 'sample and synthesis' type patches like Fairlight-type voices for instance. But my
favourite waveform has always been number 33 which gives lovely synth and string sounds.
The main selling point of the VS was 'Vector Synthesis', which employed a joystick to alter
the mix between the 4 digital oscillators in real time or via a mix envelope, which allowed
the user to store 5 positions for the mix between the 4 oscillators, to define the
rates of change between these positions and the choice of looping or repeating these changes.
This was quite an innovation which allowed highly dynamic sounds to be created, by for example
choosing 4 radically different waveforms and moving the mix between them.
In addition, the modulation matrix allowed the user to send the two low frequency
oscillators (LFOs), key velocity or aftertouch, etc. to modify the mix between pairs of
oscillators to create even more complex sounds. This could be combined with setting all 4
oscillaors with different levels of detuning and for instance using one LFO to create subtle
vibrato on one pair of oscillators and the second LFO to create vibrato on the other two.
Highly
'organic' sounds are thus possible. I have noticed that I can hear lovely 'beats' when playing
chords using some sounds, more reminiscent of true analogue synthesizers than the more sterile
newer digital models. Also the filters give a fineness and a very bright treble without being
overpowering, which to me beats the 'virtual analogues' I own, hands down. One feature from the
earlier Prophets which is missing however, is the lovely pulse-width modulation (PWM), but
there is plenty here to satisfy!
Another strength of the VS is the ability to stereo pan pairs of oscillators, and then
to alter the mix between them using the LFOs for instance. The stereo positions of the 8 voices
can also be defined independently. The VS therfore has a very strong stereo sound which can
also be varied over time to give wonderful 'swirl' to its sounds. This may partly explain why
the VS has been a favourite for film soundtracks since the 1980s.
My favourite feature of the Prophet VS is its Curtis analogue filters which give it
a great advantage over most 'S&S' keyboards, giving resonance and self-oscillation and those
gorgeous Prophet analogue filter sweep sounds.
This combination of features makes the VS a versatile synth and one with a unique feature set.
In my opinion the unusual and inventive feature set will lead to some unique sounds.
Altogether, about 2000 Prophet
VSs were made, which fall into 1 main 'revision' with 2 sub-revisions of
the operating system, 1.1 and 1.2.
They all had Curtis
Electro-Music [CEM] electronics: digital oscillators & envelope
generators, analogue filters & amplifiers.
Prophet-VS
Revisions:
Rev 1.1 Serial. Nos. ? :
Rev 1.2 Serial. Nos. ?
: Increment/decrement functions using program buttons 0, 1 and 2 to
substitute for the data slider if desired.
To increase value, select it, then hold
0 and press 2 repeatedly (or hold to 'scroll' up).
To increase value,
select it, then hold 0 and press 1 repeatedly (or hold to 'scroll'
down).
Prophet VS images: more to come soon hopefully!
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At lower left, you can see the vector joystick for dynamic mixing of the 4 oscillators
A, B, C and D, plus the silver rimmed Master Volume and Balance knobs, the (missing!)
data slider and the beautifully sapphire blue LCD display.
Upper row controls are for Oscillators, Filter, Envelope Group, LFO Group, Modulation,
Voice Control, and Chorus, with the 100-program RAM Catridge (so '80s!) beyond.
Lower row controls are for Keyboard Mode, Program Select (with 2-digit 'Program' patch number
LED display to its left), Arpeggiator, MIDI and Pitch (master tune), with a Modulation Matrix
diagram at the far right.
Modern synth makers could learn a thing or two from this lovely
machine, especially the sensible combination of accurate digital oscillators and analogue filters
and the wonderful, easy-to-use yet feature-packed arpeggiator.
By the way, I am playing 'Afterglow' by Genesis in the second photo (taken on 9th March 2001).
Being a mad Genesis fan,
I find this synth can really capture their essence, since it can do many of those classic
Prophet-5, Prophet-10 and ARP Quadra sounds which epitomise the 'Duke' era around 1980,
as well as being able to play the kind of stong, real, characteristically 'synthesizer' solos
that were a trademark
of Tony Banks' keyboard playing from about 1973 onwards. If you are a fan, you'd know what I
mean - if not, then you would probably be well impressed with this synthesizer anyway!
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The Oscillator Waveform Mix control at left controls the relative amounts of
each of the 4 chosen oscillator waveforms A,B,C and D, that are present in the sound.
This control can be used 'live' to alter the waveform mix, but is most versatile when
used to define the 'Mix Envelope.' For each of 5 points on this envelope,
named 0, 1, 2, 3 and 4, you can define an oscillator mix. The LCD display shows you
the amount of each oscillaor A, B C and D present (in percent) as you move the joystick.
In its central position, the amounts are all equal ie 25% A, 25% B, 24% C and 25% D.
Move fully to one corner of the 'diamond' and you will get 100% A for instance and
0% of the others. There are many combinations and you can hear the sound if you play a key.
Once you set the Oscillator mix for each point inthe Mix Envelope, you can set the rates so
the sound moves betweent hese points. You can also make this envelope loop on itself,
giving a cyclical chanfge to the mix! It's brilliant, but takes a while to do.
The Balance L/R knob is like a hi-fi balance control, simply defining whether there
is a bias towards the left or right stereo channel for the final sound. Usually this
will be set to its centre position as here.
The Master Volume of course defines the loudness of the overall final sound.
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The removeable RAM Cartridge is a real bit of '80s chic!
It allows you to store up to 100 patches (in addition to the 100 on board the synth).
You can also set 'write enable' or 'write protect' to prevent you from accidentally
erasing your crucial sounds!
The Modulation Matrix diagram infront of the RAM cartridge shows the Modulation
and Control Routing options available on the Prophet VS. There are plenty of them.
The modulation sources are LFO1, LFO2, Pressure, Velocity, Keyboard (tracking),
Filter Envelope and Modulation (Mod) Wheel.
The destinations are Frequency (of an oscillator?), Filter (cutoff frequency),
Mix (between oscillator waveforms A<->C or B<->D), LFO, Amplifier, Pan (stereo)
and Chorus.
This means for instance, you can use LFO1 to control the mix between oscillators A & C,
with LFO2 controlling the mix between oscillators B & D. You can also use the LFOs to pan each
oscillator across the stereo stage individually, to frequency modulate each oscillator
individually by a given amount, and/or to modulate the filter cutoff frequency for a classic
Prophet-5 type filter sweep sound, or choose other mod sources to do these things. That's
before you even start to use the Chorus!
Don't forget folks that you can also set the position of each of the synthesizer's
8 voices individually on the stereo stage, which means that as you play notes, they
can each appear in a different place in the stereo mix.
The thing about this synth is that the Mod options aren't so extensive as to be
incomprehensible. There is an individual panel button for everything, more or less, so you
can set these things to be all "OFF" and then start from a simple sound.
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