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Korg Mono/Poly

MP-4 monophonic Synthesizer (1981)

korg mono poly

"After the realease of the Polisyx, korg offered another classic synth with 4 VCO and special paraphony " 


KEYBOARD a 44 keys compact keyboard (no velocity) with wooden end panels, 41 pots for tweaking sounds, 6 buttons and 13 small switches. On the left controls for overall portamento and detune, and a switch for transposition (an octave up or down).
->In 2020 Behringe made clone of the mp4, the behringer monopoly

KEY ASSIGN a special feature of the mp4 is the voice assign, a bit different from classic monophonic:
- Unison stacks all 4 VCOs
- Unison / Share assign all voices available
- Poly four voice in polyphonic paraphony, which means mp4 share one common VCA and VCF envelope
- Chord mode, like old Poly-800, allows to record a chord and play with a single note

1-Clock input for arpeggiator (pulses)
2-pedalswitch input for portamento mode
3-VCF cutoff CV input
4-VCO FM CV input
5- gate input switch between +15V and s-trig modes
6-Trigger (gate) input
7-Trigger (gate) out
8-Control voltage pitch input  of course MONO (1V/Oct not usual Korg Hz/V)
9-Control voltage pitch output (1V/Oct not usual Korg Hz/V)
10-headphones output
11- main mono output



SOUND subtractive all analog with four VCOs based on SSM 2033 with 3 shapes: triangle, sawtooth and square wave with variable and modulable pulse width +  1 white noise generator circuit. VCO octave range is 16 ', 8', 4 'and 2' , and each oscillator has indivifual volume control and tune pot (about 50 cents).

One of the most interesting (and unique) features of the Mono/Poly is the sync ("Syncro")  and  cross-modulation ( "X-Modulation")  options between the 4 oscillators. In Syncro and X-mod Single mode, the VCO1 is the master  syncing the other 3 VCOs to it . In Double mode, both VCO1 VCO2 are masters, syncing VCO3 to VCO1 and VCO4 to VCO2.

FILTER  Punchy 4 slopes resonat Low pass filter based on classic SSM 2044, with key tracking option (150%  doesn't work with external CV control)

ENVELOPE: 2 EGs for VCA and VCF type 4 segments ADSR. Different retrig mode for EG (Single and multimode)

LFO main modulator MG1  is assigned to MOD wheel with triangle and sawtooth  shapes, 0, 1-20 Hz frequency range, and can modulate VCO pitch, filter VCF and pulse width. A second modulator MG2 (only triangle shape) is simpler.

ARPEGGIATORRange: 1 oct, 2 oct or full with  UP or DOWN or UP / DOWN direction and LATCH mode

Korg monopoly

Korg Mono/poly specifications

Brand: Korg
Model: mono/poly or Mp4
Date Produced: 1981
Country: Japan
Type: analog keyboard
Keys: 44 no velocity (F-C)
Osc Sync: yes 2 modes
Polyphony: 4 Voices
Oscillators: 4X VCO shapes: triangle / sawtooth / pulse
LFO: 2 modulators
Filter: LPF with Envelope
Envelope: 2 EGS for VCA and VCF

Tuning (Master Tune x 1, ±50 Cents or More,
Tune x3, ±50 Cents or More)

VCF Cutoff Frequency Adjustment
Resonance Adjustment
Envelope Generator
Modulation Sensitivity Adjustment
Keyboard Tracking (O -150%)

VCA EG Attack Time  Decay Time  Sustain Level Release Time 
VCF EG Attack Time Decay Time Sustain Level Release Time 
Single/MuItipIe ON/Off 

Frequency (Below O. IHz to above 20Hz)

Wheel: Bend (Sensitivity Adjustment, VCO I/Slave VCO, Pitch, VCF) 
LFOMG-1  Below O. 1Hz to above 20Hz
LFo MG-2 Below O. 1Hz to above 30Hz

Arpeggio Trigger In (GND)
Portamento( GND)
VCF fcM In (—5V +5V)
VCO FM In (—5V +5V)
Trigger In
CV In (Oct/V)

Trigger Out
CV Out (Oct/V)

Arpeggiators: YES with external clock sync
Control - CV/GATE and CV Filter
Power Consumption: 28 watts
Weight: 12 kG
Dimensions: 744mm(w) X 450mm(d) X 144mm(h)

video demo

Do you use this machine ? do you like it?  Let us know in the comment field just below 




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Pictures from

Brochure from Korg webiste


korg Monopoly Korg monopoly Korg classic vintage Synthesizer 44 keys from 1981 with 4 powerful VCO 123456789 1234567890123
90 out of 100 based on 1 user ratings
1500 to 2000 from 1 sellers Sellers:
Product description: A very underrated synthesizer, with a lot of modulation and metallic sync options, arpeggiator is truely a must for real time jam! Customer reviews:
A rare prototype - by , May 14, 2020
5/ 5stars