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Korg Mono/Poly Legacy Edition

Software Synthesizer By Gordon Reid
Published August 2007

Korg revisit their classic Mono/Poly synth in the Legacy Collection Analogue Edition 2007 - but how does it measure up to the original?

Korg Mono/Poly Legacy EditionI reviewed the original Korg Legacy Collection in April 2004, and I was impressed. Up to that time, many soft synths had been little more than pretty pictures draped over fairly standard digital signal processing, but Korg and a handful of other manufacturers, notably Arturia and Gmedia, have been in the process of raising the bar considerably, releasing soft synths that, for some uses, are indistinguishable from the instruments on which they are modelled. Foremost among these are Korg's recreations of their own MS20 and Polysix. OK, if you raise the resonance to maximum and make the MS20EX go 'thwipp', you can hear differences between the soft synth and its hardware inspiration, but claims by analogue anoraks that digital recreations 'sound nothing like the original' are untrue, and can safely be ignored.

Since then, Korg have extended and repositioned the Legacy Collection, by removing the Wavestation from the original configuration and combining it with a recreation of the M1 to form the Legacy Digital Edition. Happily, the faux-analogue side of things has not been allowed to flounder, and to the MS20, Polysix and effects that comprised the bulk of the original collection, Korg have now added a Mono/Poly soft synth to create the Legacy Collection Analogue Edition 2007. Since we have already covered the MS20 and Polysix emulations (SOS July and August 2004), this review will focus on the Mono/Poly emulation.

Korg released the original MP4 'Mono/Poly' analogue synth in 1981. The world didn't go bananas for it, although it sold moderately well. In stark contrast to the reverence in which it is now held, the Mono/Poly made hardly a ripple in a world that was still dominated by powerful American polysynths. Many players (myself included) tried it, and wondered why we should be interested in a monosynth with four reasonable oscillators and a high-quality filter when there were Odysseys and Minimoogs available, both of which offered gorgeous oscillators and legendary filters. Or, for that matter, why we should be interested in a 'paraphonic' four-voice polysynth when there were truly polyphonic six-voice Polysixes and Juno 60s to be had (see the 'Polyphonic Vs Paraphonic' box for more on the difference between these terms). It seemed that the Mono/Poly failed to excel at anything.

Of course, new forms of music create new perspectives on existing instruments. Nowhere is this more apparent than for the Roland TB303, which was transformed almost overnight from an annoying, whiney little box into a classic of the acid-house revolution. Whereas, in 1985, things that went squelch were naff, in 1995, they were cool and desirable. So maybe it was inevitable that the Mono/Poly would be re-evaluated, and that it would eventually become one of the most desirable of all Japanese monosynths.

The Technology

When Korg announced that the new Legacy Collection would contain the Mono/Poly soft synth, I heard several people ask, 'given that the Polysix is already in there, what's the point?' But, underneath their control panels, the Mono/Poly and the Polysix have little in common apart from their SSM2044 filter chips. For example, the oscillators in the Mono/Poly are SSM2033s, while those in the Polysix are Korg's own. Elsewhere, the envelope generators in the Mono/Poly are Korg's own discrete designs, whereas those in the Polysix are based on SSM2056 chips. And then there are the effects: modular-style sync and cross-modulation on the Mono/Poly, and a chorus ensemble on the Polysix. Clearly, the two instruments are very different, so it's valid to model both.

The Oscillators & LFOs

The four oscillators on the Legacy synth do not precisely echo those of the Mono/Poly itself: where the originals had octave switches, the soft synth has coarse tuning of +/- 24 semitones. Also, where the original had a +/- one octave global transpose switch, the soft synth has another +/- 24 semitones knob. Other than this, they are presented in almost identical fashion.

Korg Mono/Poly Legacy EditionMy first test was to set up the most basic patch possible on the original synth and the emulation (one oscillator, no filtering, square envelopes, no modulation and no effects) and compare their outputs. Comparing the sounds thus produced, the results were conclusive: the original is slightly brighter and raspier than the soft synth. I checked that this was not a consequence of overdriving anything in the analogue signal chain, but it was not. The same proved to be true for the other waveforms. In all cases, the original synth exhibited a slight, raspy distortion, which no doubt has contributed to its reputation for producing aggressive, peaky sounds.

Comparing the noise sources led to a similar conclusion. The two are similar, but the noise on the original Mono/Poly has a slightly greater high-frequency content. It's nothing to worry about, but whatever the source of the differences, my success rate at identifying which synth was which in an A/B comparison was 100 percent. Furthermore, these difference became slightly more obvious when using multiple oscillators tuned to the same pitch. However — and this is, I believe, more important — I couldn't tell which was which without having the other for comparison, and I could make the soft synth sound almost identical to the hard one by applying a little high-frequency boost and low-frequency cut using a basic EQ. Unless you have a psychotic need to make the soft synth sound indistinguishable from the original, these differences are not going to affect how you make music.

Modulation Generators

The way in which the modulation generators (MGs) are implemented on the Legacy Mono/Poly is somewhat different from those of the original synth. To be specific, MG1 on the soft synth has sprouted an extra waveform (Sample & Hold) and MG2 has sprouted a complete waveform knob. (The original only had a frequency control, and its output was merely a triangle wave that you could direct to PWM or use to clock the apreggiator.) Korg's programmers have also taken the opportunity to add MIDI sync with a wide range of options.

Polyphonic Vs Paraphonic

You should never call an instrument "polyphonic" simply because it can play several notes simultaneously. To earn this description, it must be able to shape each note independently, and without deference to any notes that may already be sounding. There are two ways to accomplish this. Firstly, you can use one or more envelope generators, amplifiers and filters for each note on the keyboard. This is the approach used in the Korg 'PS' series. Alternatively, you can restrict the number of notes that will sound simultaneously, and assign a more limited number of oscillators, filters, amplifiers and envelopes to them as notes are played. This is the approach used in almost every other analogue polysynth.

Both these methods were very expensive to implement in the 1970s, and a more affordable approach combined a multi-note sound-generation system (essentially, an organ) with a single signal path comprising just one VCF and one VCA whose responses were shaped by one (or two) contour generators. Roland coined the name 'Paraphonic' for this architecture when launching the RS505 Paraphonic Strings, although it was used by many famous keyboards, both before and after. These include the Solina, the ARP Omnis, the Moog Opus 3, the Korg Trident, the Poly800 and, of course, the Mono/Poly.


As you would expect, the bulk of the filter and amplifier sections on the two synths are laid out in identical fashion, and the Key Assign modes are all recreated on the soft synth. Likewise, the soft synth offers the single- and multi-triggering modes of the original, although the Auto Damp feature (which was a clever method of trying to overcome the limitations of a single filter on a four-voice polysynth) has been discarded. This means that it's not possible to reproduce some of the quirkier responses (ie. deficiencies!) of the Mono/Poly, but it would have been daft to retain it. Instead, you now have a synth that's 128-voice polyphonic rather than four-voice paraphonic, with Unison ranging from a single note comprising four detuned oscillators to (up to) eight notes, each comprising 16 detuned and spread voices. This allows you to create some enormous unison sounds, both in monophonic and polyphonic use.

Korg Mono/Poly Legacy EditionBefore testing what the VCF and VCA do to any signal passing through them, I decided to test what they do on each synth when the filter is self-oscillating. I set up a 1980s' syn drum 'dooo...' patch on each by sweeping their cutoff frequencies and amplitudes downward using their envelope Decay stages and, having got the frequencies and sweep times as close to identical as possible, compared the results. I was surprised: the Mono/Poly exhibited a percussive 'bump' at the start of the sound that is entirely missing from the emulation.

Reducing the filter resonance demonstrated that the two synths' activities at the onset of self-oscillation are also quite different. The Mono/Poly produces the same sound but more quietly, whereas the soft synth produces a percussive bump that sounds a little like the claves from an analogue drum machine.

Turning the filters' EG Intensity to maximum (so that the sounds swept downward from higher frequencies) revealed even greater differences. As you would expect, the Mono/Poly swept downward smoothly, but the soft synth exhibited two pronounced cycles of stray frequencies, similar to what you would obtain from a ring modulator. This is almost certainly a consequence of aliasing and, while it's not unpleasant, it's different from the original. Despite Korg's hyperbole about its Component Modelling Technology (CMT) it's clear that the filters and envelope generator responses on the two instruments are different if one approaches them in an analytical fashion.

Integration, Effects & Extras

The original Legacy Collection allowed users to stack two MS20 s, or two Polysix es, or one MS20 and one Polysix, in a two-slot environment called a 'Legacy Cell'. This allowed programmers to layer their sounds, split them, velocity-split them and control both components simultaneously using MIDI Controllers, all of which made it possible to create sounds unobtainable from either synth in isolation. The package also included (and still includes) two insert effects and two master effects slots, and proved to be a powerful and flexible synthesis environment. However, a Legacy Cell couldn't host the Wavestation soft synth. At the time, this didn't seem too strange; indeed, it made a weird kind of sense.

What is less forgivable is that, in 2007, a Legacy Cell cannot host the Mono/Poly soft synth, and I suspect that this is why Mono/Poly incorporates its dedicated effects. It's a shame that one can't stack two Mono/Poly s or combine one with either of the other synths in the collection, and I can't help feeling that makes the Mono/Poly feel slightly 'tacked on', rather than being as fully integrated as the name Analogue Edition 2007 implies.

The Effects sections add sonic possibilities that original Mono/Poly owners could only dream of.The Effects sections add sonic possibilities that original Mono/Poly owners could only dream of. On the up side, there are lots of other goodies that I haven't yet mentioned tucked away in the Mono/Poly soft synth. Some of them are now commonplace, such as riffs to audition sounds and the ability to assign MIDI controllers to on-screen parameters. Then there are the standard Global options for customising external modulation sources, micro-tuning, patch category names, and so on. Less common are the 20 default templates that provide useful starting points for creating and tweaking patches.

Elsewhere, the Mono/Poly's arpeggiator is recreated in almost its original form. However, there is another enhancement to be found here: the addition of a 'Random' mode. I have always found that random arpeggiation is the magic ingredient that adds fairy dust to many tracks, so it's more than welcome.

Another major area of expansion lies in the two slots for effects, and the 19 effects that you can insert into them. At first sight, these appear to be identical to the effects that were available in the original Legacy Cell, but they are not the same code: the effect names are different, so who knows what other slight changes have occurred beneath the bonnet.

Having said that, the changes (or not) are irrelevant. The important thing is that the effects enhance the synthesizer hugely. For example, in the late '70s I created lead sounds by playing my Korg monosynths through a stereo phaser and then torturing my keyboard mixer's inputs by setting their gains to maximum at 'mic' sensitivity. The results were harmonically complex, but unbelievably dirty, and cut through any mix. Using the integrated effects, I recreated these sounds on the Mono/Poly soft synth in seconds. Then, using the dynamic automation features, I could extend the patches to do neat things such as controlling the phaser's speed and depth and/or the amount of overdrive using aftertouch. I should have thought of this before.

Basic Patches

Of course, a more important consideration is whether the two instruments exhibit different characters when asked to produce more useful and conventional sounds. The answer, as it must be with such differing responses, is that they do. I left the resonance on each at the cusp of self-oscillation, and the sweep times as before, and passed a single sawtooth wave at maximum amplitude through the filter. The resulting sounds were different, with the Mono/Poly sounding thinner than the soft synth no matter how I set up the patch. Whether this is a problem or not is up to you; you can turn my last statement on its head, and say that the Legacy Mono/Poly is fatter and warmer than the analogue synth (which is true) and therefore combines the qualities of the original with greater body and depth (which is also true). Alternatively, you could say that the world is awash with soft synths that aim to be fat and blobby (which is true) and that it's a shame that the Mono/Poly emulation has lost some of the edgy peakiness of the original (which is also true).

Perhaps more important (for the second time) was what I discovered when I used the soft synth to recreate some simple Mono/Poly patches. I started with a simple trumpet patch and, given the differences already described, the result was surprising. Adding a little external reverb to the original Mono/Poly and a tad from the effects within the soft synth, I was able to obtain almost indistinguishable sounds from the two. What's more, it wasn't difficult. Next, I modified the patch into a classic analogue flute. No problem! A handful of simple lead and bass sounds? The soft synth remained slightly fatter throughout, but you would have to be the king of the anoraks to worry about the differences.

When I stopped worrying about the pedantic recreation of original sounds, the soft synth became even more impressive. I set up the simplest of patches on it — one oscillator, a bit of filtering, and unison of four voices with a tad of detune and spread — and the results would have graced any recording. I then added the second oscillator tuned to a major 5th and the results would have made any late '70s polysynth proud. Naturally, adding the third and fourth oscillators evoked even chunkier and more complex sounds. The Legacy Mono/Poly was already proving to be a very satisfying synthesizer...

Other Updates In Legacy Collection version 1.2.1

Although the removal of the Wavestation soft synth and the addition of the Mono/Poly are by far the most significant changes in the new Legacy Collection, there are a few minor ones that may interest you. There's improved support for Korg's Kontrol 49 controller, improved integration of the MS20iC controller when used with Legacy Cell, and the added ability in all modules to make your own sounds and controller maps the defaults loaded at start-up. But, for me, the most important of the changes (other than the addition of the Mono/Poly) is the addition of six new modulation sources in the MS20 software. Nice one!

Masses Of Modulation

Not only are there more voices in the Legacy emulation of the Mono/Poly; the complexity of each is increased to an almost astronomical degree. Nowhere is this more apparent than in the Virtual Patch section, which is what Korg calls its Modulation Matrix (see screen, opposite). There are eight slots (four in group 'A' and four in group 'B'), each offering 159 mod sources and 35 destinations, with bi-polar intensities for many. The original Mono/Poly didn't even offer delayed vibrato!

The Effects Section

If there was one area of sound generation that set the Mono/Poly apart from its peers, it was its arcane 'Effects' section. There was no reason for it to be arcane, but Korg chose to obfuscate its operation with strange and inappropriate names. For example, it was described as a 'One Touch' effects section. Whatever you think that this might mean, it probably doesn't... it was simply Korg's way of saying that there was an on/off switch for the whole section!

Korg Mono/Poly Legacy EditionAt its most basic level the Effects section was a combination of oscillator sync and cross-modulation (FM), which could be used singly or in combination. The complexity was added by its ability to modulate the slave oscillator (using your choice of Modulation Generator 1, the filter contour generator or pitch-bend) in two modes: VCO1 as master and VCOs 2, 3 and 4 as slaves, or VCO1 as master to VCO2 plus VCO3 as master to VCO4. All this, and you could still use the MGs and EGs to produce conventional pitch changes and filter sweeps — at the same time.

Given that analogue FM is a mighty unpredictable beastie that never sounds quite the same twice (even when produced using identical settings on two analogue synths of the same model), I had no expectation that complex patches created on the original Mono/Poly and the soft synth would sound the same. Imagine my shock, therefore, when the first patches I created sounded almost identical. Admittedly, the sounds diverged as I added complexity, but many of the Mono/Poly's endearing traits — such as the dramatic changes in sync sounds when you combine them with PWM — are retained. At extreme settings, the soft synth doesn't have the aggression of the original — in particular, the maximum depth of modulation on the soft synth is equivalent to around 8/10 on my Mono/Poly — and the differences in overall brightness tend to come to the fore here but, nonetheless, this is good stuff.


When I tried to 'break' the Mono/Poly soft synth, I generally failed. Occasionally it failed to load first time, and it crashed once or twice when I over-stressed it, disappearing from my screen without a by-your-leave, but it seems pretty robust for a v1 piece of software. I could manage to overload the processor, but that took 40 simultaneous voices (!) on a close-to-minimum-specification host computer. This is fantastic, especially when you compare it to the ARP 2600 emulation I reviewed last year, that ran out of puff with just three voices playing.

Sonically, the Mono/Poly soft synth seems to be a slightly less accurate reincarnation of its forebear than are the MS20 and Polysix emulations that complete the Analogue Edition. This may be a comment on the software, or it may reflect the vagaries of my individual Mono/Poly, MS20 and Polysix synthesizers. But I'm not sure whether I care. I was never the biggest fan of the original Mono/Poly, and the greater warmth and flexibility of the soft synth appeal to me more than a perfect recreation may have done.

As for the Analogue Edition 2007 as a complete package, it remains excellent value for money. I must admit that I preferred the original configuration of MS20, Polysix and Wavestation, because the breadth of sounds was greater, but I understand Korg's desire to group its recreations of its analogue synths in one package, and its recreations of its digital synths — the Wavestation and the T-Series — in another. That the Mono/Poly is not integrated with Legacy Cell (see the 'Integration, Effects & Extras' box) is a disappointment, but not one that would stop me from buying the package.

Bottom line? Soft synths have come a looong way in the past three or four years. While there are still some things that the analogue originals do better, you would have to try hard not to be impressed by the Legacy Collection Analogue Edition


  • The Mono/Poly emulation doesn't sound precisely like a Mono/Poly; it's fatter and warmer (many people will like this).
  • Mono/Poly is a true polysynth, with a huge increase in flexibility and sonic power.
  • Excellent built-in effects.


  • Some people won't like the fact that Mono/Poly doesn't sound precisely like the original.
  • Mono/Poly is not integrated with Legacy Cell and, therefore, the MS20 EX and Polysix EX components within the Legacy Collection.


Between 1978 and 1981, Korg released many seminal synthesizers, of which the MS20, Polysix and Mono/Poly are prime examples. Today, you can emulate all three for a fraction of the price of any one of them. Of course, you lose the knobbiness of the originals, but for sheer sound-generating value-for-money, it's easy to recommend the Legacy Collection Analogue Edition 2007.


£119 including VAT.

Korg UK Brochure Line +44 (0)1908 857150.

+44 (0)1908 857199.