Korg Mono/Poly (1981–1984): The Analog Bridge Between Monophony and Polyphony

Name: Korg Mono/Poly
Brand: Korg

A four-voice analog synth with a flexible voice architecture. It does polyphony, unison leads, and a few things in between, and it came out before digital took over.

Overview

The Korg Mono/Poly was a quiet revolutionary in the early '80s synth boom. It sold for $1,395 in 1981 (roughly $4,300 today). For that money you got true analog polyphony with per-voice voltage-controlled oscillators, filters, and amplifiers, all in a space-gray Japanese chassis. Competitors were either monophonic or prohibitively expensive polyphonic systems. The Mono/Poly sat in between: affordable for working musicians, and good enough to land on records by Depeche Mode, New Order, and Gary Numan. It filled a gap in the market that almost no one else was touching.

The four-voice architecture is only half of it. The other half is how you can use those voices. You could stack all four VCOs into a single unison lead, which is thicker than a slab of Chicago deep-dish. You could split them into duophonic mode for fat basslines with intervallic movement. Or you could go full 4-voice polyphony for chords with warmth and slight imperfection, the kind of organic drift that digital synths would spend the next decade trying (and failing) to emulate. That flexibility made it a favorite among synth-pop pioneers who needed one keyboard to do leads, pads, bass, and atmospheric textures.

Specifications

Synthesis Type	Analog subtractive
Oscillators	4 VCOs per voice, selectable tuning modes (mono/unison, duophonic, 4-voice poly)
Waveforms	Sawtooth, square/pulse (variable pulse width), triangle, noise
Filter	1 VCF per voice, 24dB/oct resonant low-pass (based on IR3109 chip)
Envelope Generators	2 ADSR envelopes (one for filter, one for amplifier)
LFO	1 LFO with triangle, square, sample & hold waveforms, with delay
Keyboard	44 keys (F to F), velocity and aftertouch sensitive
Aftertouch	Channel aftertouch (not polyphonic)
Memory	32 patch memories
Dimensions	990 mm × 375 mm × 115 mm
Weight	18.5 kg
Audio Output Level	1 Vrms max
Audio Output Impedance	1 kohm
Power Requirement	AC 120V / 230V, 50/60 Hz, 25W
Country of Manufacture	Japan
Original MSRP	$1395 (1981)

Key Features

Four-voice architecture with flexible voice assignment: The Mono/Poly’s core brilliance lies in its ability to morph between mono, duophonic, and polyphonic modes. In unison mode, all four VCOs per voice lock into a single note, creating a lead sound so thick it could stop a bullet. Duophonic mode allowed two-note playing with independent voice allocation—perfect for fifth intervals in basslines. And in full polyphony, it delivered genuine four-voice analog chords, each with its own filter and amp envelope. This wasn’t paraphony; this was the real deal.
Per-voice VCO, VCF, and VCA: Unlike budget polysynths that shared filters or envelopes across voices, the Mono/Poly gave each voice its own complete signal path. That meant every note in a chord could have its own envelope contour and filter response, resulting in a dynamic, expressive sound that felt alive. The IR3109-based filter—a chip also found in the Korg MS-20—added a creamy, slightly aggressive resonance that cut through mixes without turning brittle.
Velocity and channel aftertouch on a 1981 synth: This was advanced for its time. Most synths in 1981 didn’t even have velocity, let alone aftertouch. The Mono/Poly’s 44-note F-to-F keyboard responded to both, allowing for expressive swells and modulations via aftertouch-triggered LFO or filter sweeps. It wasn’t polyphonic aftertouch (that luxury wouldn’t become common until the Sequential Circuits Prophet-5 Rev 4), but channel aftertouch was still a major step forward in performance expressiveness.
32 patch memories with instant recall: In an era when most synths required manual knob-twiddling for every sound change, the Mono/Poly’s 32 memories were a godsend. You could store complex unison patches, modulated pads, or snappy basses and recall them instantly—critical for live performance. The interface was straightforward: numeric keypad, “Write” button, and a single LED to confirm storage. No menus, no scrolling, no nonsense.

Historical Context

The early 1980s were a crossroads for synthesizers. The monosynth era, dominated by the Korg MS-20 and Minimoog, was giving way to polyphony, but true analog polyphonic synths were either rare or ruinously expensive. The Sequential Circuits Prophet-5 had proven it was possible, but at nearly $3,000 in 1981, it was out of reach for most. Korg's answer was the Mono/Poly, aimed at affordable, expressive polyphony. It didn't try to match the Prophet-5's eight voices or full programmability. It offered four voices, a streamlined interface, and a price that made studio owners nod instead of faint.

The Mono/Poly had fewer voices, but its oscillators had a slight instability - some might call it "drift" - that gave chords a living, breathing quality. It wasn't a flaw. It was texture. Korg followed up with the budget-friendly Korg Poly-800 in 1983, which used a cost-reduced architecture with a single shared VCF. The Mono/Poly remained the last of Korg's fully-featured, per-voice analog polys before the digital era hit. By 1984, the Yamaha DX7 had arrived, and FM synthesis began to eclipse analog warmth. The Mono/Poly was produced until that same year.

Collectibility & Value

Today the Korg Mono/Poly is rated "high" in desirability and "uncommon" in the wild. In 2025, a fully functional unit in good condition will fetch between $2,500 and $4,000 USD. Mint examples command the upper end, especially with the original case and documentation. Its value has steadily climbed, not just for nostalgia, but for its sound: a slightly gritty analog tone that modern plugins still struggle to replicate.

Buyer beware: age has not been kind to all units. The most common issues are capacitor leakage and power supply failures, particularly in the AC/DC converter board, which can take out other components if neglected. Sticky keys and worn keybed contacts are also frequent, because the rubber pad contacts under the keys degrade over decades. When shopping, look for a unit that powers on without hum, has responsive aftertouch, and retains tuning stability across all four voices. A recapped power supply and cleaned key contacts can add hundreds to a synth's resale value, but they're often necessary.