Moog Polymoog analog polyphonic synthesizer
Last Update 04-19-2010
The Polymoog was a pioneering design when it was released in 1975 - and
by 1977 was an orphan because of its stellar reputation for
unreliability and because progress had surpassed it. The other
well-deserved common complaint was
that the Polymoog didn't sound like a Minimoog. In the early
1970s, polyphony was a tough nut to crack. The prevailing
technology before today's accepted voice assignment polyphonics were
perfected was the top octave divider systems (TOS) which dates back to
organs in the 1950s. String machines such as the ARP String
Ensemble or Crumar String Performer were at heart a TOS system.
Bob Moog designed a polyphonic rank module for Wendy (ne' Walter)
Carlos in 1969 that was a TOS system. The Polymoog represents the
peak of TOS system design (although it is a Dave Luce design, Bob had
little to do with it). TOS gives you full polyphony - every key
has its own note. Unfortunately what you can do with this note is
a very limiting factor in the Polymoog.
Dave Luce (pictured here
on the right with an early production unit)
designed the Polymoog, which began prototype life as the
which was featured on ELP's "Brain Salad Surgery". Bob Moog had
little if any design input as his duties under Norlin removed him from
development. Luce was something of a perfectionist which was
evident when the Polymoog needed a staggering 200 engineering changes
before it was ready for production. Internal memos show a company
trying to pin Luce down and freeze the design, to force it to closure
and get it in production. I have seen a drawing of an alternate
panel design, no less confusing than the one we know today. Luce
also was fond of complicated
convoluted designs where a simple
would have done the same job. If you don't believe me, I dare you
to make sense of the Polymoog block
diagram. Any EE who has
studied both volumes of the service
Luce will hardly dispute this.
There were six Polymoog prototypes built with a 72 note keyboard with a
C to B range. Chick Corea and Larry
Fast each had one of these prototypes. The production Polymoog
changed the range
to E, then feedback from musicians competing with guitarists
changed it to a E to D
keyboard and reduced it to a 71 note
to an E/D range required a tooling change that was expensive. It
had the longest Pratt-Read production keyboard
and each keyshell was
filled underneath with epoxy and leadshot to give it a weighted
feel. While it doesn't feel anything like a piano, it's actually
pleasant to play. Pratt-Read never made an 88 note keybed to my
knowledge, their target industry was organs not pianos.
Moog developed a promotional movie about the Polymoog. It
features interviews and performances with Dave Luce, Michael Boddicker,
Chick Corea, and Herbie Hancock as well as a goofy stop-action
animation involving a Polymoog in a wooded knoll with two mimes.
Roger Luther of Moog
Archives offers this movie converted to disc.
When the Polymoog was released, the buzz was afoot and everybody wanted
one. It had a touch sensitive keyboard, was fully polyphonic, and
you could change sounds without re-configuring up a panel full of knobs
and switches. Remember, this was 1975 and nobody else had a
synthesizer that offered these features. It was the first
synthesizer with a piano sound that was velocity sensitive, but as you
read below the velocity sensing system had a fault.
There is confusion regarding the model names of Polymoogs. When
released in 1975, the eight
preset version with a panel full of
slidepots (model 203A) was badged the Polymoog Keyboard. When
Moog released the economical fourteen
preset version (model 280A) it
became known as Polymoog Keyboard while the eight preset fully variable
version was re-badged Polymoog Synthesizer.
Presets named "strings", "piano", "organ", "harpsichord", "funk",
"clav", "vibes", and "brass" comprise the 203a
while the 280a
"vox humana" (made famous by Gary Numan in his hit single "Cars"),
"string 1", "string 2", "electric piano", "piano", "honky tonk piano",
"clav", "harpsichord", "brass solo", "brass chorus", "pipe organ",
"rock organ", "vibes", and "funk". I never liked the "Funk"
preset on my 203a and I replaced the wimpy thin "piano" and "organ"
with sounds of my own, which necessitated calculating preset resistors
and soldering them in. "Brass" isn't very authentic or fat
either, especially with the limitation of a master filter.
Polymoogs had velocity sensitive keys, which was big BIG news in
1975. However the velocity sensitivity had a serious flaw.
If you held down the sustain pedal and repeatedly pressed the same key
at light velocity, each repeated key press would result in louder
volume. The velocity voltage had an accumulative effect when you
repeatedly pressed a key with the sustain pedal held down. This
isn't very practical for percussive sounds like piano. In
practice I rarely use the velocity feature.
The description below applies to the 203A Polymoog (I never owned the
Despite the "fully variable" tag, you cannot store custom patches on a
Polymoog. There is no microprocessor under the hood. When
you push a preset button, CMOS switching merely selects fixed resistors
which configured the sound. If you want to tweak the sound,
changing the slidepot doesn't do anything until you press a VAR button
that makes the slidepots live. The VAR button merely replaces the
fixed resistors with the resistance element in the front panel
slidepot. Pressing the accomodating PRE button reverts back to
the fixed resistors and restores the preset configuration. If you
ever played with a Prophet 5 Rev 1 or Rev 2 polyphonic synthesizer that
has PRESET buttons, this convention originated in the Polymoog.
As primitive as it would appear, this design is not ancient. The
ARP ProSoloist of 1972 used a similar fixed resistor design although it
did not offer user tweaking.
In normal operation, pressing a preset button toggled the VAR buttons
to PRE so that the preset configuration was called up. There is a
button on the selector panel marked with a dot labeled PART/FULL.
When you pressed this button, a period would appear in the LED.
If you manipulated the sound using VAR buttons and changed to a
different preset, the VAR buttons would retain their state. This
is useful if you have an envelope setting or filter setting you wanted
share across one or more presets. One other trick I discovered -
if I press and hold the PIANO preset then press BRASS, the BRASS sound
would use the PIANO preset mode filter (see below), which can offer
some variety to the sound.
The best approach to tweaking sounds is to use a preset as a starting
point, then tweak the sound to your liking.
The technology for storing patches had not yet progressed to the
microprocessor patch storage system of today because microprocessors,
RAM memory, and ADC/DACs were very expensive back then. Oberheim
devised their patch storage system using RAMs and ADC/DACs by 1975 in
the SEM polyphonics, and microprocessors weren't implemented until 1977
in the Prophet-5.
The early Polymoogs were temperamental beasts and were extremely
unreliable. Thanks to Luce's penchant for fancy circuits, the
same principle of mechanical systems applied - the more moving parts,
the more likely it will fail. The Polymoog was chuck full of
fancy circuits which had a habit of malfunctioning. Moog had a
lot of Polymoog returns for warranty repairs, and that cuts into their
bottom line. Today the mere mention of "Polymoog" strikes fear
and dread in musicians who had to endure them breaking all the
time. The same could be said for repair shops, and few techs will
touch a Polymoog today. It is the rare Polymoog today that is
Polymoogs of serial number 3900 and higher did implement a set of
reliability improvements at the factory. My unit is 4XXX and I
can confirm that it has survived years of club gigging with few
problems. My unit is dated October 1979 under the hood and is
badged "Polymoog Synthesizer", so if you want a later reliable unit
then avoid the ones that are badged "Polymoog Keyboard". Judging
by the history of ebay auctions, these later units seldom appeared.
How does a TOS system work? If you divide a periodic waveform by
two, the result is an octave lower. A TOS system is a "rank"
consisting of a master high frequency oscillator that is divided into
the 12 semitones of the highest octave of desire, then the descending
octaves are achieved by dividing by two each of those 12 semitones in
succession. The complete rank is a "voice" in organ terminology,
as opposed to the accepted convention of the synthesizer single note
"voice". Every single note in a rank is firing
continuously. However the waveform of each divider output is a
pure square wave. The Polymoog implements waveshapers per key (to
be discussed below) to create ramp and variable pulse waveforms.
The Polymoog is a two rank TOS system - one rank of ramp waveforms and
one rank of variable pulse waveforms.
Because the master oscillators in each Polymoog rank are independent,
they can be detuned. And therein lies a major limitation of
synthesis on the Polymoog - only the master oscillator can be
modulated, not the individual notes. You cannot pitch modulate
individual notes in a TOS system.
The other major limitation in the Polymoog TOS system is
filtering. The VCF is a single master filter for all the
notes. If you apply a spiked EG to the filter and then stagger
the notes in a chord, the VCF will spike for note 0 then note 0+1 then
note 0+1+2 then... pretty useless for brass voicings. While
keyboard tracking can modulate the VCF, it isn't very practical in a
master VCF system because when you hold a chord then release succeeding
high notes, the keyboard tracking for the high notes isn't reset to low
notes unless you retrigger the low note.
The ad copy does boast of each key having its own filter - while this
is correct, it is not practical. The Polymoog has a custom made
"Polycom" IC for each key. This Polycom IC has two waveshapers
(converts the square waves from the dividers into ramp and variable
pulse waveforms), two VCAs, a mixer, an envelope generator, and a two
pole ladder filter. There, each key does have a filter
right? But the front panel provides no control over the filter,
it is configured by preset resistors under the hood. The Polycom
filter has no resonance capability at all, and there is no facility for
modulation - not by an EG, an LFO, nothing. In fact the
schematics refer to it as the "brightness" filter, and that is the best
description for it.
The lack of filter resonance and modulation in the Polycom doomed the
Polymoog in the sound palette department. Why didn't Moog
implement it? Remember that back in the early 1970s, customized
ICs was unheard of and expensive. A lot of R&D went into the
Polycom, and compromises had to be made for the technology of the
day. They had to keep the pin count on the IC package down, and
filter resonance and modulation increased the pin count to the point
the cost was unrealistic. Considering that the Polymoog
originally listed for $5295 in 1975 dollars, this is not hard to fathom.
The reason for the limited palette of the Polymoog's TOS design is
because it cannot implement voice modulation - if you wanted to
modulate the VCF or the PW using the oscillator of an independent
voice, you could not do it. Want to modulate the pitch of a
single note in a TOS? Can't be done. The effects that can
be done on the Polymod section of Prophet-5s or voice modulation
section of Memorymoogs
are not possible on the Polymoog.
Contrast to the accepted synthesizer architecture of
VCO->VCF->VCA per voice, the Polymoog architecture is
VCO->brightness filter->VCA per key. Then the Polymoog
audio can be processed by preset filters (called "mode" filters), by
the master VCF, or by a "Resonator" (the model 280A Polymoog Keyboard
omits the Resonator). The filtering is done in parallel and there
are separate outputs for each filter system on the rear panel (but not
the 280A). There is also a DIRECT output that bypasses the filter
so you can hear the "brightness filter" in action (and witness how thin
and wimpy it sounds). You can also use the direct output for
Two VCOs are offered. VCO#1 is ramp only and can be switched to
8' and 4' ranges while VCO#2 is variable pulse only and can be switched
to 16' and 8' ranges. The Ramp waveform can be detuned and its
level is variable, but not the pulse waveforms. There are three
master LFOs available - two for frequency modulation (one for each
ramp/pulse rank) and one for pulse width modulation. This is one
of the few saving graces of the Polymoog as it works to create nice
string or vocal pads.
There is a LOCK button that syncs the ranks together. But it is
not hard sync, it is phase lock sync. Phase lock sync locks the
VCO pitches exactly. If you attempt to use the detune control,
both ranks will change in pitch and stay in sync. Hard sync is
much more interesting in that detuning the synced VCO creates new
timbres. Due to the TOS architecture, hard sync is not possible
(the dividers can only create pure square waves). In LOCK mode,
the frequency modulation is converted to phase modulation. But
the phase shifting is a wimpy sounding single stage phase shift and has
little effect on the sound. You can hear the phase shift in the
The "Mode" filters are preset filters which are standard electronic
opamp textbook filters, some are simple 12dB low pass and others are a
mix of 12/24dB LP/BP/HP. These are NOT the famed Moog transistor
ladder filters and they are not editable.
The Resonator is a three-band multimode filter system - it is NOT the
Moog parametric EQ, totally different circuit. It is not the
famed Moog transistor ladder filter either. Each band covers
low/mid/high ranges and has level, frequency, and resonance
controls. There's a switch that changes the filters from lowpass
to bandpass to highpass, on all three bands at once. While this
sounds interesting, Luce blew it because the filters are 6dB/oct.
The 6dB/oct Resonator is a standard electronic textbook state-variable
filter, and it isn't as useful or colorful as the 12dB/oct Oberheim
state-variable filter. The 6dB/oct passes too many harmonics,
resulting in a buzzy sound even at maximum resonance. It isn't
very useful for formant sounds because there aren't any overlapping
frequencies between the bands. The Resonator can't be modulated
The master VCF *is* the Moog transistor ladder filter but it sounds
pretty lame, in fact of all the Moogs I own this one is the worst
sounding Moog filter of the lot. It also won't
self-oscillate. Why? It's the last device in the audio
chain, there's no post VCA to kill the oscillating VCF when you let up
on the key. Remember, the Polymoog is VCO->brightness
filter->VCA *per key*, THEN to master VCF. That's another
reason why the Polymoog has no noise source.
Thanks to its generous rear panel, you
could process external audio through the mode filter, the resonator, or
the master VCF. The 280a had a less generous rear panel.
There is a panel section for the loudness contour generator, which
controls the envelope generators in the Polycom ICs. It is the
ADS/shared-D/R system similar to the Minimoog (this is
"progress"?!?). You have separate DECAY slidepots for upper and
lower splits, which is really limiting when you read the paragraph
regarding bi-timbality. The EGs have a flaw - if the ATTACK time
is greater than the DECAY time, you get next to no envelope and near
silence. The LOCK button engages the release stage of the EGs,
same as holding down the sustain pedal. You don't want this
engaged all the time because the unit will slowly build up a high
frequency hiss in the audio.
Some ad copy claim that the Polymoog is bi-timbral. Very limited
bi-timbrality, actually. Remember - master VCF limits the
bi-timbrality. You can split the upper and lower section (split
point is fixed at two octaves above the lowest key). Each split
has control over waveshape selection, frequency modulation, pulse
width, PWM, ramp level, decay time, and which section is processed by
which filter system. If you wanted a spikey bass in the lower
split with a mushy pad in the upper - can't be done because you don't
have separate ATTACK controls for each split. Also the keyboard
has three sections whose audio can be balanced with three slidepots but
again not very practical. Occasionally I use these balance
slidepots to get some overdrive in the audio.
Nevertheless both versions are capable of making some unique and
exceedingly powerful sounds. While they should not be dismissed,
you should also be prepared for the price of admission as any used unit
will need TLC and $$$ to get it in top shape.
A common complaint (rightly justified) was that the Polymoog didn't
sound like a Minimoog.
Luce had a different approach to sound
than Bob Moog. Bob exploited distortion while Luce adhorred
it. Luce put more focus on circuit stability and control than he
did on sound, IE great pains were taken to ensure minimal distortion in
the signal path. The reason the Minimoog sounds so good is the
subtle distortion from overdriving the filter and VCA, and because Luce
neglected that the sound of the Polymoog is too clean. You can
crank the levels with the BALANCE sliders next to the mixer section but
the distortion isn't at all pleasant, it's not the same effect as
overdriving the Minimoog filter.
An optional foot pedal controller called the Polypedal
285a) was available. This was a substantial unit with two
sweep pedals, two foot pedals, three footswitches, and two thumbwheels
on the rear. The unit connected to a Polymoog with a multicable
snake that fanned out into plugs. I had replaced these fanned
cables with a multipin connector and replaced the TRIGGER IN jack with
the mating connect. TRIGGER IN on the Polymoog was rather
impractical and not used in my applications. One sweep pedal
controlled volume, the other could control pitch or filter
cutoff. One of the thumbwheels will adjust the amount of pitch
bend. One of the footpedals controlled sustain while the other
could control trigger mode (single or multiple triggering).
Frankly I found the latter not very useful. The footswitches
selected sweep pedal destination to filter or pitch, and a third EXT
SYN enabled triggering of external syntesizers. You could use the
Polypedal on other Moog synths like the Minimoog, Micromoog, Multimoog,
anything that had the six pin cinch-jones "accessories" power
connector, although the Minimoog will need to be modified to provide
5DVC for the Polypedal.
What's this "external synthesizer" bit? You mean the Polymoog
keyboard can be used as a CV controller for my modular? Yes,
*BUT* not across the full 71 keys. The Polymoog keyboard is split
at two octaves above the lowest key, and this split point can't be
changed. You can use the keyboard as a CV controller with either
the lower 24 keys, or the upper 47 keys. A shame you can't use
the entire 71 keybed at once. However glide and pitch ribbon does
work on the external CV output.
Yes folks, the Polymoog is in effect a fancy organ. It's a dual
TOS system with PWM and VCA per key, and a few master filters thrown
in. Despite its promising technology, it quickly became
outclassed and even derided in many circles.
Moog had their share of teething problems with the Polymoog and it
became an orphan with the competing synths. It also gained a
reputation of unreliability (it is the rare Polymoog that is 100%
functional today and few repair shops will touch them). Then the
assignable voice polyphonics that followed - Oberheim FVS Four Voice
SEM in 1975, Yamaha CS-80/60/50 in 1976, Prophet-5 in 1977, Oberheim
OB-X in 1979 - showed the world the superior implementation of
polyphonic synthesis. Yes there was the Yamaha GX-1 in 1975, but
these were prohibitably expensive and less then 70 of them were
made. Moog finally discontinued the Polymoog in 1980 and released
the Memorymoog in 1982 - a pretty late entry in an already crowded
market! Alas, before the Memorymoog could establish a foothold,
the Yamaha DX-7 effectively killed the analog synthesizer market in one
The Memorymoog was a
worthy successor to the Polymoog in that the
assignable voice system is the superior polyphonic design. There
are a lot of tricks in that are not possible in a TOS sytem like
the Polymoog, chief among them voice modulation. That is why the
Memorymoog has a broader palette of sounds over the Polymoog.
The Polymoog was my first Moog synthesizer and my first endeavor in
polyphonic synthesizers, the velocity and full polyphony appealed to me
as a piano player. But it didn't take long to learn of its
limitations. Strings, pads, organs, and harpsichord are the
Polymoog's specialty - and that's about it. I bought my Polymoog
synthesizer with Polypedal, legs, and case in 1985. Later as I
acquired my other moogs (Source, Memorymoog, Minimoog, Taurus, Voyager,
etc) the Polymoog got used less and less. Being my first moog
synth, I'm too attached to it to sell it and it's been with me for many
gigs. It's still in really good cosmetic shape and it looks great
in the studio. At one point it served my studio as a coffeetable
(good looking one too). Today I am exploring new sounds with
external processors, notably my Korg SDD-3300. I can get some
really nice vocal pads with this combination. The Polymoog is
undeniably an important instrument in synthesizer history, but it's not
terribly variable and most are not very reliable.
If you're looking for your first analog or your first polysynth, don't
pick this one.