Was it a true synthesizer and was it really polyphonic? The Polymoog used divide-down twin oscillator circuitry, (with relative detune) which wasn't dissimilar to that employed in string machines and electric organs. To some this meant that it didn't have the "characteristic" Moog sound and was somehow thinner and not the "real deal". Once again, the derisory battle cries from those expecting a polyphonic Minimoog. As previously mentioned, this wasn't Luce's intention...







So what was it capable of? Both oscillators could be detuned against each other and the Polymoog offered sawtooth and pulse/square waves, (although limited to certain keyboard split zones). In addition pulse width modulation was also available. Oscillator 1 was ramp only and could be switched to 8' and 4' ranges and oscillator 2 was variable pulse and was switchable between to 16' and 8' ranges. The oscillators could then be passed through what Moog rather grandiosely referred to as "Resonators". In fact it was really just a three band equaliser but with variable gain, frequency and resonance (similar to a parametric). The Polymoog also had a 5 channel mixer on the control panel for the direct output of the preset, filter, resonators and the lower and upper halves of the keyboard - providing facilities to layer each section of the sound. In addition, each section had a separate output for external processing. The Polymoog had ample output options; Trigger outputs controlled external monosynth's and there were three inputs that allowed you to pass an external sound source through the Resonators and the VCF.

So what about the "presets"? Once again this was a misconception. Luce claimed that the Modes, (remember - he didn't call them presets) were supposed to be a "starting point". For instance if Piano was selected, this would be set up to offer the correct percussive envelope and tone of a piano sound but then the operator was supposed to then use the VAR mode to modify the sound to taste with the synth section. What made the Modes different from simple presets derived from the front panel controls was that each mode was generated by dedicated chips containing 142 circuits known as articulators.












The articulators consisted of 71 amplifiers and 71 filters that shaped the sound from the oscillators. In effect the articulators contained the fundamental timbre of each sound. This clearly explains why some of the new "presets" available on the 280a Polymoog Keyboard were difficult or impossible to reproduce on







the original 203a, simply because the dedicated articulator circuits were not available in the 203a.

As I mentioned earlier, Polymoog's had a Moog ladder filter but there was only the one so this part was technically monophonic. The filter did offer a dedicated ADSR, variable cut off, resonance. In addition, it also provided two modulation sources, (LFO and Sample and Hold). There was also a separate velocity sensitive VCA and envelope for each note so it was polyphonic, well, kind of…



Depending on the trigger option selected, when sustaining a chord and then playing an additional note, the new note would either trigger all of the other notes being held, or would have no filter articulation. If it was played using the "Mode" output and the controls were left in their "Pre" states, you could actually play it in true polyphonic fashion. In practice though, you would almost certainly use the final VCA, VCF and Resonators, which would produce what would be more accurately described as "Paraphonic". I believe this is because compromises had to be made. As if the Polymoog wasn't already expensive, bulky and complicated enough… to add a separate filter and envelope for all 71 notes would have been unviable, not to mention an immense physical challenge. Corners invariably had to be cut and rather than offer limited polyphony found in the 4, 6 and 8 voice polysynth's that were just around the corner, Luce decided to use the divide-down dual oscillator method to achieve his objectives... the worlds first fully polyphonic synthesizer. Whether









he accomplished this or not is a matter of divided opinion but... yes! all 71 notes on the Polymoog can play simultaneously, something which is still rare even now, 30 years later.


© Shaun Brooks 2005