You are here

Korg Legacy Analogue

Software Synth For Korg OASYS By Gordon Reid
Published April 2007

The MS20EX oscillators and filters page looks almost identical to the panel of an MS20. The Parameter Details panel in the lower right-hand corner offers complete information about any selected parameter.The MS20EX oscillators and filters page looks almost identical to the panel of an MS20. The Parameter Details panel in the lower right-hand corner offers complete information about any selected parameter.

Korg bring the MS20 and the Polysix to the OASYS and introduce a major OS update.

When Korg released the Legacy Collection in 2004, it was hardly a new concept: model the sound of a vintage synth and combine the signal-processing guts with pretty graphics that fool you into thinking that you hear something that (maybe) you don't. But the company's confidence that the Collection emulated the sounds of the originals was far from misplaced, and I gave all three synthesizer components — the MS20, Polysix and Wavestation — a resounding 'thumbs up'. Since then, a number of other manufacturers have released soft synths of equivalent accuracy and usefulness. In particular, G-Media's ImpOSCar and Arturia's revised version of the Minimoog have impressed me, and I have more than a passing fondness for Arturia's Prophet V.

Given this, and the slew of new soft synths being released in 2007, you might feel that recreating vintage analogue synths in digital form has become passé, but Korg have come up with a new twist. Taking the MS20 and Polysix soft synths from the Legacy Collection, they have not only rewritten them as two EXis for the OASYS, but have extended the models still further to create two unique instruments running on what is, in my experience, a more reliable platform than a Mac or PC trying to run a similar range of applications. Furthermore, each of these models can take advantage of everything that the OASYS has to offer in terms of sequencing, arpeggiators, real-time control, KARMA and more. This has to be of interest...

Getting Started With v1.2

The two new EXis — MS20EX and PolysixEX, collectively called 'Legacy Analogue' — are part of the v1.2 upgrade for the OASYS, but they are far from everything that the new version has to offer.

Firstly, the Unison mode has been enhanced. It now works on polyphonic sounds, and a combination of stereo spread and a greater maximum detune dramatically increases the depth obtainable from the effect.

Secondly, there's a new chord memory function. It seems that Korg's engineers felt that, if they were going to code the chord memory for PolysixEX, they might as well make it available to all the sound engines and integrate it with the velocity-sensitive pads. This makes it possible to store up to eight chords simultaneously (with independent velocities for each note), and to transpose them up and down by playing single notes on the keyboard, as in 1981.

Next, the polyphony of two of the previous EXis has been increased. I'm particularly pleased to see that the STR1 Plucked String synthesizer now offers 50 percent more voices (increased from 32 to 48) while the AL1 analogue synth has increased from 84 to 96. In addition, a new parameter — max number of notes — allows you to set the number of voices available to each of the synth engines. This means (for example) that if you want an instance of the PolysixEX to act authentically and start stealing notes when the requested polyphony exceeds six, you can make it do so. This idea is extended into the Combi and Song modes so you can have multiple Polysixes simultaneously, each acting as a true six-voice synth.

Finally, Korg claim that a new algorithm provides improved parameter smoothing (less zipper noise) when using the front-panel hardware. No longer having an OASYS running v1.1 or earlier, I can't make a direct comparison, but it seems better, especially when rotating a knob for the hackneyed high-resonance LP filter sweep.

The MS20EX

The MS20 in OASYS uses Korg's Component Modelling Technology, which the company claims models the original synth right down to component level. I have always thought that this assertion is bunkum, but I am pleased that CMT has been used; however it works, it was successful in the Legacy package, and it would make little sense for Korg to replace it here.

Now, I'm not going to re-evaluate the MS20 here, nor perform a detailed sonic evaluation of its sections as I did when I reviewed the Legacy Collection (Sound On Sound, July 2004). Nor am I going to discuss all of the features — the additional performance capabilities, enhanced modulation routings, the effects and so on — that were added at that time. Much more interesting is to ask how much further the MS20EX has been extended on the OASYS.

The MS20EX patch panel, showing the new mixers on the right-hand side.The MS20EX patch panel, showing the new mixers on the right-hand side.

The answer is 'Lots!' In particular, the patch panel has been extended to make the OASYS incarnation much closer to a modular synthesizer than the semi-modular architecture of the MS20. Korg's blurb suggests that these enhancements were inspired by the sought-after MS50 expander module, but this seems unduly modest. Indeed, Korg could say that the OASYS's MS20EX was inspired by the PS3200 or PS3300 polysynths (and it's a tempting comparison) but that would still sell it way short of the truth. As far as I am concerned, having individual patch points for each of the oscillators and the filters makes this Korg's first analogue-style, patchable, modular synthesizer.

In addition to all the new patch points, Korg have added an input that accepts the audio from anywhere within the OASYS (external audio inputs, the audio outputs, or any of the busses) and directs it anywhere within the MS20EX's patch panel. The functionality of the External Signal Processor (ESP) has also been extended, and there are two new two-into-one signal mixers, which are equally happy with audio signals and CVs. The programmers have also made it possible to direct a single output to multiple destinations, in effect replacing the MS20's quarter-inch jack sockets with 'virtual' banana plugs. Unfortunately, you can't stack cables at inputs, which is why the new mixers are so important.

You insert 'cables' by double-tapping on one socket (first to select it, and then to say that you want to use it as one end of a patch cable) and then tapping on a second to connect the two. This is slick, and you shouldn't underestimate its importance; it makes the whole interface a pleasure to use, and is far better than using a mouse or trackpad as on the Legacy Collection.

The MS20EX also features numerous additional modules available on previous EXis. Most obviously, this means there are four additional multi-stage envelope generators, four additional polyphonic LFOs, and four AMS Mixers (all of which are identical to the AL1's, except that there are twice as many of the AMS Mixers). There's an almost unbelievable amount of modulation available here; most of the MS20's parameters have two AMS sources, with one modulating the intensity of the other.

It's hard to convey in a few words just how exciting this soft synth is. Embedded as it is within the OASYS, it is not only a remarkable, polyphonic MS20, it's integrated with all of the usual EXi facilities, including the sequencers, vector control, the EQs, KARMA, and all of the OASYS's insert, master and total effects. Of these, the ability to control an MS20-style patch using the vector joystick came as the biggest surprise. To test this, I tried the obvious, and created a patch whereby the joystick controlled the filters' cutoff frequency along the 'X' axis and the amount of resonance on the 'Y' axis. The results retained the characteristic, peaky, aggressive sound of the original synth, but took it into realms that I couldn't even imagine when I was gigging with my MS20 sitting on top of a Logan String Synth in the late '70s!

Given the huge flexibility of the MS20EX, the control interface could have become somewhat cumbersome, but Korg have come up with a neat programming system that reduces its potential complexity to a manageable level. To be specific, just tap one of the on-screen knobs, and a little panel appears in the lower right corner of the screen to tell you which control is selected, its value, what AMS sources are applied, and the intensities of each. To edit any of these values, just tap on the appropriate figure and use the Value slider to edit it. Or the increment/decrement buttons, or the spin wheel, or the numeric keypad.

If this still seems a little daunting, Korg have sought to simplify things for gigging musicians (as opposed to sound designers) by providing a standard Tone Adjust configuration for the OASYS's top-panel controllers. This places the most important parameters under your fingers, just as if you had an MS20 (or the Legacy Collection 's MS20iC controller) in front of you, and is a boon if you like to tweak or manipulate sounds in real time. What's more, these are only the default settings, so if you would like to swap them around, or bring other parameters to the top panel, there's nothing stopping you from doing so.

Despite all the synthesis power on tap, the MS20EX uses less processing power than previous EXis. This means that you can allocate numerous MS20EX­based programs (each with a maximum polyphony of 48-voices) within a Combi without undue fear of causing the OASYS to choke on its cornflakes. Furthermore, as with previous EXis, the OASYS allows you to stack two EXi patches in a single program. Imagine what you can do with two of these hyper-expanded MS20s layered together. This is not trivial stuff.

Just one word of warning... Until you get to know the MS20EX in depth, you might find that some of your own patches seem to choke in unexpected ways, curtailing notes when you don't expect it. This is due to the way that the OASYS allocates voices depending upon the release time of the audio signal VCA and, by implication, the envelope controlling it. If you decide to separate the VCA from its default EG2, you need to tell MS20EX which envelope generator has the longest duration, so that the OASYS can allocate voices accordingly.

Upgrading & Evaluating

You can download v1.2 from, an American web site that provides support to owners of the OASYS and the Legacy Collection. You'll need to provide your OASYS's unique 16-character identity code for security purposes, but that's trivial. Less straightforward is the need to burn the new OS to CDs before you can install it on the OASYS itself, but I understand that Korg will provide CDs for you if you are unable to complete the standard procedure.

Unlike the STR1 Plucked String synthesizer that was contained in v1.1, MS20EX and PolysixEX are not free, although functional demo versions complete with a full bank of patches are installed when you upgrade. These versions fade in and out with a deep tremolo, making them all but useless for making music, but adequate for evaluation.

If you then choose to purchase Legacy Analogue, you provide payment details and the site will bill you $249 (around £130 at current exchange rates) for an authorisation code. Simply enter this into the appropriate place in the OASYS's Global pages to enable the new synths fully.

The PolysixEX

Two years ago, the Polysix seemed to be a strange choice for the second of Korg's virtual instruments. Without its swirly chorus/ensemble, it was a limited, single-oscillator polysynth: superb value in 1981, but nowhere near as involving as, say, a Mono/Poly or the hybrid DW8000, and far from earth-shattering in the 21st century.

The PolysixEX main page.The PolysixEX main page.

Nonetheless, this was the second analogue synth in the Legacy Collection, and it remains the partner to the MS20EX in the OASYS. To be honest, nobody should complain, because the Polysix is beautifully simple to use, and it has character. Indeed, it produces big, bold basses, and its simple but warm pads are ideal when you need a polyphonic sound that will not attempt to dominate a mix.

This simplicity is illustrated by the maximum polyphony of the PolysixEX in the OASYS: a massive 172 voices if you're doing almost nothing else with the host synth. This means that you could, in principle, run 14 simultaneous patches, each with two layers of PolysixEX at six-voice polyphony. (In practice, a maximum of 16 PolysixEXs are available, because of the way that the OASYS allocates its fixed resources.)

The PolysixEX Tone Adjust default configuration — this shows you some of the possibilities for hands-on control.The PolysixEX Tone Adjust default configuration — this shows you some of the possibilities for hands-on control.

Again, it would be superfluous to re-evaluate the Polysix and its recreation in the Legacy Collection. You can find my views on these issues in the August 2004 edition of SOS. Furthermore, there are fewer enhancements on the OASYS's version, so there's less to say here, too. In short, PolysixEX takes the Polysix, includes the additions first seen in the Legacy Collection (primarily, enhanced modulation) and then adds the standard OASYS-style EXi modules: two additional envelope generators, two additional LFOs, and four additional AMS Mixers, with AMS modulation applied (or not, as you wish) to the original synth's parameters.

Because of the simplicity of the original synth, the majority of its control panel can be represented on a single page. The exception to this is the arpeggiator, which lies on a second page alongside the External Modulation sections.

As you would expect, the programming method for the PolysixEX is identical to that of the MS20EX (sans patch panel, of course), with the Parameter Detail panel helping you to set values accurately and to keep track of the vast amount of modulation that's on tap. And, as on the MS20EX, there's a Tone Adjust configuration (as shown above) that brings almost every 1981 parameter to the top panel. Finally, as with the MS20EX, the PolysixEX also takes advantage of the OASYS's sequencer, arpeggiators, vector synthesis, KARMA, effects busses, and so on. This means that it is far more than the Legacy Collection Polysix loaded onto another platform.

Eliminating The Bugs

Given that the OASYS is, at heart, a well-programmed computer, it would be surprising if no bugs appeared when the OS was given a major overhaul, as it was between v1.1 and v1.2.

The first release of v1.2 was v1.2.1, and this suffered from a number of intermittent freezing problems. Version 1.2.2 eliminated many of these, but was superseded in December 2006 by v1.2.3 which, in turn, was immediately withdrawn and replaced with v1.2.3 (!) about a week later. This fixed another handful of minor bugs and is, I believe, the most stable OASYS OS to date.

Nonetheless, there are still a handful of issues to address. For example, there's one in which, if you remove Unison from a patch but don't save it, jump to another mode to do something and then return to Program mode, the Unison sound is restored, but the button stays unticked. It took me a while to work that out, and it illustrates how fiendishly complex a modern workstation can be.

However, lest you get the wrong idea, the OASYS is in my experience less buggy and more stable than any Mac or PC that I have used for music, and Korg are to be congratulated if this is the worst problem that v1.2 will throw at you.

The Reality Of Virtuality (Or Not)

For the first time since I started to review soft synths, I haven't set up the original instruments next to their emulations. You may find this somewhat remiss of me, but I see no reason to believe that Korg have messed with the guts of the Legacy Collection, and I suspect that the differences between the OASYS's DACs and the soundcard in your Mac or PC will be just as significant as any changes in the software itself.

However, there's an even more important reason why I don't deem it necessary. The MS20EX and PolysixEX synthesizers have advanced so far that any comparison is almost meaningless. Yes, it's nice to know that MS20EX can emulate the grittiness, distortion and occasional instabilities of the MS20 (which it can), but it would be daft to base a conclusion of its worth on this. I prefer to think of MS20EX less as a polyphonic MS20 than as a powerful new polysynth that is made more usable by a control panel that I grew to love (and hate) in 1978.

This viewpoint is just as appropriate to the PolysixEX because, for many applications, it feels and responds much like the original, and the simplicity of its user-interface should draw even the most reluctant owner into programming new sounds and experimenting with existing ones. Again, it's great that the soft synth has the sonic character of its vintage inspiration, but once you start to delve into the AMS modulation and start to make full use of the additional EGs and LFOs, the fact that it can sound almost identical to a 26-year-old tub of analogue chips, capacitors and resistors should almost be viewed as a bonus rather than a raison d'être.

If I had to find a caveat (and it's hard to do so) it would be that there's so much going on behind the scenes that some owners of the original synths may find it hard to unlearn the limitations of analogue technology and get to grips with what's possible in 2007. But, let's be honest, that's hardly a criticism of either MS20EX or PolysixEX!

Why Buy Legacy Analogue?

Before getting my hands on MS20EX and PolysixEX, one of my first thoughts was 'Why bother?' After all, every OASYS comes with the AL1 virtual analogue synthesizer, and despite a somewhat unfriendly user interface, this is a stonkingly powerful instrument.

But having had access to v1.2 for a few weeks now, I can suggest two more reasons why the MS20EX and PolysixEX should find a home on every OASYS. Firstly, there's the sound. The AL1, MS20EX and PolysixEX all sound different, just as three different models of analogue synthesizer sound different. Secondly, there's the, well, attitude that comes with an analogue-style user interface. The new EXis have it; the older one does not. I can see myself reaching for the MS20EX and, in particular, the PolysixEX time and time again in precisely the way that I don't reach for the AL1. I'm pretty sure that you'll find the same.


I have been a fan of the OASYS almost since the day it was announced. Its development represented a bold move by Korg, and I still view it in the same light as the Yamaha GX1 or GS1 — expensive keyboards that did something better than it had ever been done before, and which became the precursors for whole ranges of future products.

Of course, with the addition of the MS20EX and PolysixEX in v1.2, and the release of the spin-off M3 workstation at NAMM, it's possible that some at Korg might feel that the OASYS has now fulfilled its aims. Happily, this is not the case. On my recent visit to Korg's HQ in Tokyo, I asked a roomful of the company's senior staff whether their attention would now turn elsewhere. "Absolutely not", they assured me; the development of new Korg products in other areas does not in any way diminish the amount of effort being applied to further enhance the OASYS's capabilities. It seems that work on the platform continues apace, and that further upgrades and enhancements are already in development.

So, for now, what of v1.2?

Let's be clear: every user should upgrade to this version because the improvements in the OS itself are worthwhile and free of charge. As for MS20EX and PolysixEX, if you own an OASYS, you have to buy these. If you don't own an OASYS, you're going to lust for one more than ever before. 


  • Version 1.2 offers numerous improvements for every OASYS.
  • MS20EX is a stunning and deeply engaging polyphonic synthesizer.
  • PolysixEX is simpler, but warm and useful in almost everything that it does.


  • Nothing significant that I have found... except that you need an OASYS to benefit from it!


For no price at all, v1.2 improves your OASYS in four ways, with a new chord memory function, improved unison, improved polyphony for STR1 and AL1, and less zipper noise when controlled by hardware. For just £130 more, it adds the remarkable MS20EX and the beautifully straightforward PolysixEX, both of which are superb soft synths in their own rights. If you've already shelled out a few thousand quid for the OASYS itself, I can find no case against spending a fraction more to take it to yet another level.



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

+44 (0)1908 857199.