Korg Ms-20 (1978)

"Ms" was acronym for "Monophonic Synthesizer" born just after the famous "PS" family (polyphonic synthesizer) production.

Today it is considered as a big vintage classic Hated or loved mainly for the distorted harsh filter... still worth a buy?

KEYBOARD Black little synth very compact and portable about (8 Kg) featuring a 37 DO-DO with no Velocity keys. It features a single modulation wheel generating +/-5 Voltage and a nearby button switch for trigger or re-triggering some synthesis functions on main patch panel.
This Japanese machine is overall well built with 38 featured pot knobs quite precise and reliable in time... maybe the keys tends to get "clunky" in time.
The main panel has no less than 35 patch connection like a modular to interrupt the pre-routed signal, however the Ms-20 is not "modular" and often called "half-modular" (I do hate this term) let's says it' s a synthesizer with some external routing signal even if some synthesis section are path fixed.
All knobs functions are organized with different drawn sections featuring some strange captions, and may soon results in confusion, so a little effort is required to tame the black box ... you would not buy an Ms-20 just to randomly turn Cutoff, WON'T YOU?

VOICE Monophonic analog synthesizer featuring two analog Oscillators (no sync between) with variable octaves height each with own Volume mixing.
Let's deep this:

- VCO1: octave range from 32' to 4' has four possible Waveforms Triangle / Saw /Pulse with variable duty % Width PWM / white Noise.
- VCO2 has higher octave range from 16' to 2' but has less waveform options Saw / Square / Ring modulator (as waveform) / fixed 25% Pulse lacking PWM and replacing it with a Pitch detune +-5 semi tone range.
The Mastertune potentiometer affects both VCOs pitch while and Portamento speed adjusts the note Legato play.

VCF multimode VCF with two serial filters: One Voltage-controlled High Pass featuring two pole slopes, and a Low Pass one with also two poles.
Both filters can be combined to obtain the famous "Screaming filter" with Band Pass or notch-reject results and Cutoff pot can be also driven by patching CV section with CV IN VCF LP and CV IN VCF HP and / or Envelope 2 (EG2). Both VCFs have independent Resonance Emphasis potentiometer called "Peak" that reach self-oscillation (a nice sinusoidal).
This particular and screaming VCF is the most interesting aspect of the synthesizer and results perfect for electro music and various noise creations, even if sometimes you never know precisely what you will obtain turning the black knobs ... beware of high-frequencies? it is now so famous that the Ms20 VCF has been "cloned" many times, in particular in a wonderful filter box called "Frostwave Resonator" with many CV controls.
Another interesting VCF feature is that External inputs can be filtered through the double filter with a dedicated section called ESP "External Signal Processor" complete with Envelope Follower (the same featured in the Korg Ms-03) and a pitch-to voltage tracker / generator.
There are two Ms20 filter hardware versions depending on the production series: the first one is "IC 35" filters and second one has a smaller board with custom integrated chips. Some people prefer first version, but maybe this is just for price speculation as they are basically the same.

ENVELOPE two called "EG1" an "EG2". First one has three stages A/D/R (Attack Delay and Release) and second one five stages "ADSHR" Attack / Decay / Sustain / Hold (keeps Sustain before Release segment) / Release.
ADSHR is also default EG for VCA (both OSC) Amplitude, but you can also patch VCA initial gain with apposite CV patch and EG2 that define also Envelope for both VCF Cutoff.

LFO a single internal Low frequency oscillator called "MG" with progressive variable waveform from rectangular to triangular (LFO outputs 2 CV with separate LFO triangle and rectangular - at same frequency) or use an external one with TOTAL IN CV (remember to active MG T/EXT ->not<- EG/EXT).
Not exactly a LFO but there is also a SAMPLE and HOLD section for some (always useful) random / stepped modulations, and you have to patch it for yourself: usually white noise IN (better pink) and don' t forget S/H clock frequency or it won' t work (LFO Square clock CV out can do the job).
The LFO modulates at the same time VCF LP CUTOFF, VCF HP CUTOFF and VCO (1-2) pitch with internal frequency (no so high).

MEMORY none, but in the manual there's a lot of useful patch suggestion like create you oboe sound or mariachi guitar ... mmm yes... instead get pencil and download the blank patch (below), print it, and you're on the road for brand new sounds creation.

RELATED MS FAMILY :

MS-10: the little brother! with just one VCO, but still sounds good and it has some special gimmick like the PWM CV IN not featured on Ms20 - well you can actually mod it for this if you can't sleep at night.
MS-50: basically a Ms10 with totally open structure with a LOT of patching routing Input/output. Quite hard to find, maybe the rarest of the bunch after the blackboard.
SQ-10: dedicated MS sequencer, 12 steps - really "on the fly" pots! great one.
VC-10: a vocoder with some CV interaction with MS family. Sounds like a big juicy frog.
MINI Ms-20 : a remake from 2013, few informations for now... a believe that this marketing operation sucks anyway.

SPECIAL MS-20: BLACKBOARD EDITION: a special huge version of the ms-20 for synthesis learning purposes. It is quite hard to find (seems to be around 40 produced), but it has the same specs of standard MS20: I think it's worth only if you're a rich collector because it's pretty awkward to use.

100% ms20 sounds!

sequence with peak sample and HOLD 1 sample and HOLD 2 Mg modulation Mg RING madness minisong demo (thanks to andy matic )