Korg MS-20

Korg MS-20 owned by musician Steve Law

The Korg MS-20 is a patchable semi-modular monophonic synthesizer which Korg released in 1978. It was part of Korg's MS series of instruments, which also included the single oscillator MS-10, the keyboardless MS-50 module, and the SQ-10 sequencer.

Although the MS-20 follows a conventional subtractive synthesis architecture of oscillators/filter/vca, its patch panel allows some rerouting of both audio and modulation, and it includes an external signal processor. This flexibility lead to its resurgence during the analog revival of the late 90's.

Audio path

Oscillators

The MS-20 has two VCOs, which both include triangle, square and ramp waveforms. In addition, one of the VCOs has a "ring mod" setting which is in fact an exclusive-OR between the square wave outputs of the VCOs. The other VCO output can be taken from the noise source. Although the pulse width of VCO1 is adjustable, there is no voltage control for this parameter and as a result pulse width modulation is not possible. The VCOs have Hz/V voltage control inputs.

Filters

There are two VCFs. Both VCFs are 12dB/oct Sallen-Key designs. Resonance ("peak" in Korg parlance) is adjustable but not voltage-controlled. The VCFs are connected in series, high-pass first and low-pass second. This allows both voltage controlled band-pass and notch responses to be constructed.

Output

The final component in the audio path is a VCA.

Modulation

Envelopes

There are two envelope generators. EG1 has Delay, Attack, and Release parameters, whilst EG2 has Hold, Attack, Decay, Sustain and Release. The envelope generators have S-trig trigger inputs.

Other sources and options

The MS-20 also includes an LFO with ramp up and down, triangle, square, and various pulse waveshapes. There is a noise source, a separate modulation VCA, a wheel controller, and a trigger button.

Musicians who have used the MS-20

The MS-20 has been used by bands such as Air, 'Da Skoda's' and OMD. Aphex Twin likes to put many of his sounds through the ESP (External Signal Processor), which is also used by Mira Aroyo of Ladytron. Goldfrapp also uses an MS-20.

Nicole Skeltys of Biftek and Steve Law of Zen Paradox and others played in a MS-20 only improvisational group called the MS-20 Arkestra in Melbourne on 6/6/06.