Korg MS-20 Mini Analog Synthesizer Review
By Francis Preve
Tue, 12 Nov 2013
Ask any vintage synth fan to list their top ten analog wants, and you’ll find the Korg MS-20 on that list. Introduced in 1978, the original MS-20 has been used by countless electronic artists from Depeche Mode to Daft Punk to Aphex Twin. Rumor has it that William Orbit loved the sound so much that he relied on the MS-20 extensively to process his recorded audio as well as many of his other synths. With its combination of gorgeous and gargantuan filters, true modular patching options, and an honest-to-goodness pitch-to-voltage converter, it’s no wonder that a pristine MS-20 can command as much as two grand on eBay. That is, until Korg blew the doors off the vintage synth market by re-releasing a brand new, true analog MS-20 in a slightly downsized form factor—and at a price in the range of us mortals. The new MS-20 Mini is an absolute analog game-changer. Here’s why.

PROS: True analog. Massive-sounding filters. Modular patching options abound. External signal input for processing audio through filters and VCAs. Pitch-to-voltage converter allows controlling the synthesis engine with other instruments.

CONS: Filter envelope implementation is a bit confusing. Non-standard Hz-per-octave implementation makes it tricky to interface with other voltage-controlled synths.

Bottom Line: A must-have, true analog, semi-modular legend that’s priced for everyone.

$719 list | $599 street | korg.com 




The MS-20 architecture truly stands the test of time in terms of both sonic flexibility and ease of use. The signal path is fairly standard—two oscillators into a pair of filters into a voltage controlled amplifier—but its execution is unique. Technically the MS-20 Mini is a semi-modular synth, which means that you don’t need to use the patch bay to get it to make sounds. However, you can opt to, overriding the default signal path for deeper sonic experimentation.

Each oscillator offers a slightly different set of options. Oscillator 1 includes triangle, sawtooth, and variable-width pulse waves, plus a noise generator. Oscillator 2’s waveform options are sawtooth, square, narrow pulse and “ring mod,” which is actually derived from a combination of the two oscillators’ pulse waves but in practice sounds quite similar to true ring modulation.

The oscillator levels are controlled by a simple mixer, which in turn feeds a pair of resonant filters in series: a highpass followed by a lowpass. Hardcore vintage geeks will be pleased to know that the lowpass filter circuits are based on the original MS-20 filter, designed in-house by Korg. It’s worth noting that later in the run of the original MS-20’s production, Korg switched to an off-the-shelf filter circuit that wasn’t quite as beefy, so the duplication of the original circuit is a big plus of the MS-20 Mini.

At this point, we should delve into the sound of the filters, because while other vintage synths—notably the Roland Juno-6 and Jupiter-8—also include highpass and lowpass filters in series, nothing in the history of analog sounds quite like the MS-20’s implementation.

For starters, the MS-20’s highpass filter is fully resonant, which means you can do a couple of really cool tricks with it. If you’re a bass fiend, maxing out the resonance and tuning the highpass cutoff to the range of your bass line delivers a massive low-end wallop, with a truly incredible overdriven character. Alternately, if you’re a fan of filter sweeps, you can hear each harmonic pop out as you slowly raise the cutoff. What’s more, the spots between the harmonics come so close to oscillation that you can use the highpass filter to add “ghost” sine wave tones, creating the illusion of an additional oscillator.

The MS-20 Mini lowpass filter is equally beefy, with the same kind of overdrive and oscillation characteristics that make you feel like the whole synth is going to explode if you push it too far. With both filters at full resonance, I was able to generate sweeps and morphing effects that were far more grungy than any other analog synth in my rig—and let’s just say I’ve got a bit of a collection going.

Modulation sources include an LFO and two envelopes. The LFO offers a cool little twist, in the form of a continuously variable waveform generator that can smoothly sweep between ramp and triangle, delivering far more clever animation possibilities than the usual triangle-square-saw trinity. What’s more, it also offers an alternate mode that utilizes a variable-width pulse instead of the ramp options, accessed via the modular section.

The two envelopes are configured slightly differently. Without touching the patch bay, envelope 1 is hardwired to pitch only and includes an initial delay time, attack time, and release time. This is great for adding everything from little pitch blips at the beginning of a sound to Afrojack-inspired “dirty Dutch” sweeps.

Envelope 2 controls the amplifier and both filters. It features the classic ADSR design with the inclusion of a hold segment—which is great for adding a bit of Moog-like punch to patches. It’s also a fantastic parameter to tweak while a sequence plays, allowing you to extend specific notes in a very musical manner.

Envelope 2 is also where things get a little tricky with the MS-20, since it’s also the hardwired envelope source for filter modulation. The wrinkle here is that the MS-20’s design is unlike any analog synth I’ve ever encountered—not necessarily in a bad way, but definitely confusing, especially for new users.

Without getting too far into the technical exotica of what’s actually going on under the hood, increasing the MS-20’s filter envelope modulation amount can actually decrease the cutoff frequency. This is because the sustain level of the filter modulation is basically inverted from a functional standpoint. That is, if you set the sustain at full for amplifier enveloping, then turn up the filter envelope amount, the cutoff frequency will be in inverse proportion (or thereabouts) to the sustain level. Thus lowering the envelope sustain level will then raise the cutoff frequency when modulation is in place.

While I was thoroughly befuddled when I first encountered this, I have to say that I’m glad the MS-20 Mini is set up this way. Why? Because it makes it an even more colorful tool in my arsenal. After all, the original MS-20 was designed during the “wild west” era of analog synthesizers—a time when there weren’t many rules and in order to stand out from the crowd, a manufacturer had to take risks. The MS-20’s unusual envelope behavior is a perfect example of this aesthetic and I’m 100 percent happy with Korg’s devotion to maintaining the integrity of the original—even if it means a bit of head-scratching at first.

Modular Tools

In addition to its stellar and utterly original sound, the MS-20 Mini is also the first truly affordable modular synth for the masses. While its implementation isn’t as comprehensive as, say, building your own modular system from scratch (as covered in our July 2013 issue), the MS-20 Mini is still capable of a wide range of analog voltage tricks that no other synth in its price range can touch. Better still, the process of discovering how now-standard synth features were originally implemented makes it the perfect educational tool—not to mention a deep well of happy accidents.

Case in point: Sample-and-hold, a.k.a. the “random” LFO wave shape known from ELP to Prince for its burbling sound. While the MS-20’s LFO is quite capable in itself, there’s no sample-and-hold waveform setting on the knob, so you have to make one yourself—by connecting the output of the pink noise generator to the input of the sample-and-hold processor, then clocking that processor with the LFO’s pulse wave output, and finally routing the sample-and-hold processor output to an oscillator or filter voltage input.

Simpler patching tactics abound, like manually patching the pitch-bend wheel to the oscillators, or taking it a step further and rerouting the pitch wheel to control the amount of envelope modulation to a given destination. You can skim across the surface or dive into some really deep waters.

Best of all, you don’t have to discover all of the MS-20 Mini’s cool tricks on your own, since Korg includes the original MS-20’s patch instruction manual. Once you get past the endearingly dated writing style of the booklet, there’s a ton of really useful patching techniques lurking within, so you can experiment with the concepts behind subtractive analog synthesis without feeling totally adrift at sea.

In addition to tons of nifty modular patch points, the MS-20 Mini also includes a truly remarkable pitch-to-voltage converter. If you’re enthusiastic about Ableton Live 9’s new pitch-to-MIDI tools, you’ll lose your mind over this vintage tech that converts any monophonic (but not chordal) audio signal into voltages that can drive the MS-20’s synth engine. For example, you can take a recorded vocal—or saxophone or flute or other synth—and use its volume and pitch information to “play” the MS-20.

Granted, it takes a little setting up to get everything working right. There are high- and low-cut filters to zero in on the most useful frequencies and it takes some detailed tweaking to get the voltages to track everything correctly, but once you’ve got that nailed, you’ll be rewarded with the ability to make almost anything you’ve recorded into your DAW into a control source for the MS-20’s synthesis tools.

Even if you’re feeling lazy and don’t want to fiddle with getting the settings right, you can still create extremely organic swoops and burbles that would take forever to draw in a DAW’s automation lanes. Regardless of your approach, this is one heck of a cherry on the MS-20 Mini sundae and a wonderful resource for electronic dance music producers and prog shredders alike.


To say that the MS-20 Mini is a must-have addition to your rig is absolute understatement. As an analog synth, it’s a stunning recreation of a big and bombastic legend. As a modular synth, it’s a treasure trove of voltage-controlled madness for pros and the perfect educational tool for beginners. As a processor of external signals, it opens up a world of options for recorded material, whether you’re just processing audio with its filters or digging deep into the pitch-to-voltage capabilities. Plus, the fact that it’s got a street price of around 600 bucks has made it one of Korg’s biggest hits in a long, long time—which is why it’s still back-ordered after several months on the market. So get in line now. The MS-20 Mini is truly “all that”—and a clear Key Buy winner.


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