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Korg MS20

Monosynth (Retro) By Norman Fay
Published November 1996

Long before the M1, Korg tried to win the hearts of synth fans with the diminutive MS20. Norman Fay steps back in time.

When you see a band or musician on the TV using synthesizers, if you're a bit sad, like me, then you probably can't help trying to work out just what kind of synths they're using. Most of the time it's not too easy — one grey oblong box looks much like another after all. There are, however, a few which always stick out a mile — the Minimoog, with its flip‑up control panel, and the Jupiter 8, with its shiny metal wedge‑shaped end panels, are examples which spring immediately to mind. Another is the diminutive and distinctly odd‑looking Korg MS20.

The VCO waveforms are very bright and clear sounding, and as an added bonus, the tuning — at least on mine — is exceptionally stable...

I assume most SOS readers know what an MS20 looks like — a three octave keyboard with a steeply rising control panel behind it in an L‑shaped black case. To the left of the panel are the various knobs, and to the right are some 35 cryptically‑labelled sockets, of which more anon. Although the MS20 looks a bit weird, the design is actually quite practical if your studio is a bit lacking in space. The machine is tall and narrow, with all of the sockets on the front, allowing you to push it right up against the wall. For live use, however, its shape is much less useful — you'd have to make a big square case to keep it in for one thing, and if you stand your MS20 on top of another keyboard and play it facing the audience, then they probably won't be able to see you!

In the past, Korg's instruments were notorious for adopting unusual solutions to the problems of synthesizer design — look at the Wavestation, for example — and the MS20 is no exception to this. Compare it to a 'classic' analogue monosynth, like a Minimoog or a Pro‑One, and on the face of it, it seems to be quite similar. When it actually comes to using the thing, though, you'll find that whilst you can actually do all of the same things, it's always in a different, and not always immediately obvious, way. Here's where it gets a bit complicated...

Characterful Filters

As its signal sources, the MS20 has two VCOs and a noise generator. The VCO waveforms are very bright and clear sounding, and as an added bonus, the tuning — at least on mine — is exceptionally stable, a far cry from some analogue synths I've had the dubious pleasure of owning! VCO1 gives you triangle, sawtooth, variable pulse — no PWM, I'm afraid — or white noise waves, whilst VCO2 has sawtooth, square, fixed pulse, or ring modulated waves. That adds up to a fairly comprehensive selection, and it's possible to use both VCOs along with noise, if you so desire. There's an external input to the filters on the patch panel, as well as a pair of outputs for pink and white noise. Both VCOs share a single pair of modulation depth knobs, one hard‑wired to envelope 1 and one to the LFO. These modulation sources are overidden by a pair of sockets on the patch panel.

... a distinctive and versatile little workhorse, which will provide you with loads of good sounds...

All of the above then goes through the VCFs — the MS20 has both high‑pass and low‑pass resonant filters, which is a great bonus in my view — and a VCA. Each of the VCFs has its own pair of modulation knobs, similar to those on the VCOs. The filters have a clean, bright quality that I personally find very pleasing. When reading up on the MS Series for this article, I grew tired of reading the same comments about the tone of the MS20 in general, and it's filters in particular, namely that it doesn't sound as "good", or as "powerful" as (can you guess?) the Moog filter — how predictable! What a dreary task playing the synthesizer would be if everything sounded the same. I think the MS20's filter is just as characterful, in its own way, as the Minimoog's. Furthermore, by using the high‑pass filter in conjunction with the low‑pass, a range of cutting lead sounds can be programmed, which will remain audible in even the muddiest mix without cluttering it up still further.

Modulating Envelopes

To modulate all of the above, you have access to two envelope generators and an LFO. Now the usual way a two‑envelope analogue synth is laid out is to have a pair of ADSR type envelopes, with one hard‑wired to the VCF and one to the VCA — nothing so obvious for the MS20, of course! Envelope 2 is the 'standard' one. As well as the usual knobs for attack, decay, sustain, and release, it has an additional one which holds the envelope open for up to 20 seconds — useful once in a very long while! Envelope 2 is hard‑wired to both the VCA and the VCFs — even here there's a bit more to confuse the unwary synthesist. The signal envelope 2 sends to the VCFs has its sustain level set at zero volts regardless of the other parameters' settings. The practical effect of this is that if you programme a contour with the sustain set to full and turn the VCF envelope depth control up, then nothing happens until you turn the sustain level down, and the further down you turn it, the more effect the whole envelope contour has — what were Korg thinking of? Thankfully, the control voltage sent to the VCA is more conventional. Otherwise, you'd be hard pushed to get the damn thing to make any noise at all most of the time.

Envelope 1 is a simpler affair than 2, with knobs to control the attack and decay times, as well as one to delay the onset of the whole contour by up to 10 seconds. This envelope is hard‑wired to the oscillators, for pitch sweeps, and can also be used to delay the onset of the LFO via the patchbay. The LFO is fairly standard, but for the fact that it has a variable waveform control, which either controls the width of the pulse wave, or the shape of the triangle/sawtooth wave, depending on which you're using.

To the right of the panel, amongst the patchbay sockets, are a few more bits and pieces — another VCA, designed for controlling the level of CV signals; a sample and hold module; a noise generator with pink and white noise; and the external signal processor. The latter allows the user to take any sound, shape it using the processor's low and high cut filters, and extract CV and trigger signals from it. This, on my MS20, actually works very well — it even tracked an electric guitar reasonably well, although the use of a compressor is strongly recommended. A handy trick when using the processor is to feed the output signal through it, which gives you the oppurtunity to do some further tonal shaping, or to overload the processor's filters for a 'fatter' sound — if you must!

Patch Work

Now we come to the part of the MS20 which sets it apart from most other monosynths — the patchbay. Don't think for a minute that you're getting a 'proper' modular synth here — the signal flow is fixed. Both VCOs go through the high‑pass VCF, followed by the low‑pass VCF, then the VCA, and there's nothing you can do about it. All of those jack sockets are purely to patch in the various modulation options. Now I'll have to be honest here, and say that if you're using an MS20 on its own, you don't really gain that much in what you can do. For example, on my Roland SH09, if I want to set up a delayed vibrato effect, I'll set the vibrato depth and rate controls to the settings I want, and then adjust the LFO delay slider until it sounds right — all very simple. Now here's what I have to do on the MS20. First patch the LFO out to the input of the modulation VCA, then take the mod VCA's output to the mod input of the VCOs, then take the output of envelope 1 to the control input of the mod VCA. Only then can you twiddle the knobs until you hear the effect you want. A bit of a faff, and don't ask how to set up a random LFO effect — I only have so much space!

The MS20 has another advantage over many other monosynths — almost all of its electronic components are easily available.

I shouldn't be too harsh on this aspect of the MS20. It's actually a lot of fun to play with if you know what you're doing. I'm glad it wasn't my first synth, mind — I rather doubt I'd have got very far with it! Where the patchbay comes in useful is when you use the MS20 with either another MS Series synth or a proper modular instrument. Bear in mind here that the MS20, like all of Korg's monosynths (except the Mono/Poly), uses Hz/volt control voltages instead of the more common octave/volt standard, and will thus be incompatible with most other old analogue synths. There are a couple of ways around this problem, though. You can use the external signal processor for a partial solution, or you can use the interface box Korg made specifically for this purpose, although you'll need good luck to find one!

Sounds Like...

I'd better say a few words here about the MS20's sounds, although I'm starting to think that perhaps too much fuss is made these days about the different sounds various old synths can make. Surely it's the music that's most important? In any case, apart from a few really distinctive instruments, such as the Minimoog or the EMS synths, most, if not all, old analogue instruments sound very similar, and once they are recorded and mixed, I'd defy anyone to tell a Pro‑One from an SH2, an ARP2600, or whatever. Heresy for the analogue nut perhaps, but I'll bet most readers agree with me. Anyway, the MS20, like most analogue synths, can produce most, if not all of the chunky bass and sequencer sounds you'd wish for, as well as the whole repertoire of bleeps and twiddly Tim Blake/Hawkwind sound effects. Where the MS20 scores is when you start using its high‑pass VCF, which enables it to produce a range of beautiful, delicate, reedy leads — perhaps not the most fashionable of sounds, but I find them very inspiring to play.

Best of all, it's common enough to be reasonably priced.

The MS20 has another advantage over many other monosynths — almost all of its electronic components are easily available. Whenever I've had an old synth in the past, I've always ordered the repair manual from the manufacturers — if they're still around — and checked on the availability of spare parts, so that in the event of problems I can get it fixed. I must confess that generally any instrument which uses 'hard to find' parts, such as the older SSM chips or Curtis chips, I'll sell pretty quickly, because I don't need the hassles of trying to obtain and paying inflated prices for rare, 'out of prodution' components. Where the MS20 scores is that most of its chips are standard, easy to find devices such as the 4558 and 071 op‑amps. I can't stress how important this is for the user. As an example of how bad it can get, my Roland SH09 uses a special double transistor called a ua726. I tried to get one to keep as a spare, but I was unable to locate one anywhere. I have since found out that the 726 is available, but only as a military spec part costing over £100! This is by no means the highest price you'll encounter for rare electronic parts, either. There are a few tricky parts for the MS20, but it's nowhere near the worst, so this machine at least can be bought with some confidence.

Distinct Versatility

If I appear to be damning the MS20 with faint praise here, then I suppose it must be because it isn't, by any stretch of the imagination, a 'classic' instrument. Nonetheless, it is a distinctive and versatile little workhorse, which will provide you with loads of good sounds, and is unlikely to let you down. Best of all, it's common enough to be reasonably priced. You shouldn't have to pay more than £350 from a private seller, and a scan of the SOS classifieds over a two or three month period should turn one up, if you're interested.

Meet The Rest Of The Family...

Almost as common as the MS20 is its little brother, the MS10. In every way a cut‑down version of the 20, it has only one VCO (although you do gain pulse width modulation), one envelope (given the unusual character of the 20's DAR envelope, this is not such a limitation as it might appear), no high‑pass filter, a shorter keyboard, and a much sparser patch panel. It doesn't sound anywhere near as good as the MS20, but it is still quite characterful and seems to sell quite cheaply on the second‑hand market.

The MS50, which is much rarer than the 20, is a keyboardless expander, with a whole bunch of handy synthesis functions spread across its front panel. It has a VCO, a low‑pass VCF, a VCA, two envelope generators — one standard ADSR type, and one with hold, decay, attack, and release parameters as well as a trigger delay. There's also a good voltage controlled LFO, a little three into one mixer, a ring modulator, an octave divider, an 'integrator' (portamento — I think!), an invertor, and a cute little voltmeter. The MS50 is obviously an excellent companion to either an MS10 or 20, or, in fact, any old synth — the VCO works with octave/volt as well as Hz/volt control signals. Unfortunately, it was rather expensive when it came out, so it sold poorly. Consequently today, it has a collector's value far in excess of its real worth as a musical instrument. What a shame.

The SQ10 is a 12‑stage analogue sequencer — the old Tangerine Dream type, with rows of knobs. Undoubtedly lots of fun to play with, but unfortunately, the same comments about collectors value/musical value apply to this one too.

The VC10 is a real weirdo — a vocoder in the same 32‑key casing as the MS10, with a goose‑neck microphone sticking out of the top of it. I had a play on one a few years ago, but I must confess, I wasn't too impressed with it. If you find one cheaply enough though, do have a go.

There are also a few little 'widgets' in the MS Series:

  • MS01, a modulation footpedal
  • MS02, a useful little Hz/volt to oct/volt convertor
  • MS03, a pitch to CV convertor, similar to that fitted to the MS20.