ARP Omni 2 (1978–1981)

A 49-key slab of analog warmth that drips with chorus-soaked strings and growling bass—one of the last great preset synths before the programmable era took over.

Overview

Turn it on, hit a chord, and within three seconds you’re swimming in that unmistakable ARP chorus—thick, swirling, and slightly surreal, like audio dipped in liquid amber. The Omni 2 doesn’t ask for programming chops or menu diving; it just works, delivering lush, cinematic textures straight out of the box. This isn’t a synth for tweakers who want to sculpt waveforms from scratch. It’s for players who want to play—to lay down a bed of strings under a guitar solo, punch in a fat monophonic bassline, or float a soft pad behind a vocal. And it does all three at once.

Under the hood, the Omni 2 is a hybrid beast: part string machine, part analog polysynth, part monosynth—all sharing one keyboard but operating in parallel. The String section uses divide-down oscillator technology, similar to the Solina or Eminent 310, giving it that classic, slightly glassy ensemble character. But unlike those European string machines, the ARP flavor is creamier, less brittle, with a subtle low-mid warmth that sits beautifully in a mix. The Synthesizer section adds a true analog voice path—24dB/oct low-pass filter, ADSR envelope, triangle LFO—with a single oscillator waveform that can be toggled between quasi-sawtooth and a hollow square via the "Hollow Waveform" switch. Then there’s the Bass section: monophonic, with its own simple ADR envelope and dedicated output, capable of deep, rounded tones that feel more musical than the typical synth bass of the era.

What makes the Omni 2 special isn’t just its sound, but its architecture. It’s “paraphonic” in a way that predates the term—each note triggers the same envelope and filter for the synth section, so rapid passages lose articulation, but sustained chords bloom with a coherence that feels organic. The keyboard is 49-note, non-weighted, with a bus-bar triggering system that’s electrically quirky but robust when maintained. And the build? All-steel chassis, ARP’s signature orange-and-black faceplate, and a rear panel that offers separate outputs for Strings, Synthesizer, and Bass—what ARP called “Tri-phonic” operation. Run each through its own effects chain, and you’ve got a modular setup in a single box.

It wasn’t the most flexible synth ever made, but in 1978, it didn’t need to be. At a time when most players were still using organs or Mellotrons, the Omni 2 offered instant, reliable polyphony with zero programming. No patch memory, no MIDI (not originally, anyway), no digital displays—just sliders, switches, and sound. And a lot of it.

Specifications

Manufacturer	ARP Instruments, Inc.
Production Years	1978–1981
Original Price	$2,495
Keyboard	49 keys, non-weighted, organ-style
Polyphony	49-note (Strings and Synthesizer sections)
Timbrality	2 (Strings + Synthesizer, plus monophonic Bass)
Oscillators	Divide-down (Strings), Single VCO (Synthesizer), Single VCO (Bass)
Waveforms	Quasi-sawtooth, Hollow Square (switchable via "Hollow Waveform")
Filter	24dB/oct Voltage-Controlled Low Pass Filter (Synthesizer section)
Filter Envelope	ADSR (Synthesizer), ADR (Bass)
LFO	Triangle waveform, routed to VCF cutoff
Effects	3-Voice Chorus Phaser (patented ARP circuit)
Outputs	Strings (main), Synthesizer (aux), Bass (aux), Chorus Phaser (front panel switchable)
Inputs	Gate & Trigger Out, VCF CV, ADSR Release
Keyboard Trigger	Single or Multiple Trigger selectable
Construction	All-steel chassis
Weight	70 lbs (31.8 kg)
Dimensions	38.5" x 14.5" x 6.5" (97.8 x 36.8 x 16.5 cm)
Power	115V AC, 60 Hz (with voltage converter for international models)
Color Scheme	Orange and black control panel

Key Features

The Chorus Phaser That Defined an Era

ARP didn’t just slap on a chorus—they patented one. The 3-Voice Chorus Phaser circuit in the Omni 2 was a major upgrade over the original Omni, with a smoother, more dimensional sweep and a slightly slower rate when engaged with the Synthesizer section. This wasn’t just modulation; it was spatial alchemy. The Strings section runs through it by default, creating that signature “moving” sound—like a string section recorded in a cathedral with slowly rotating speakers. Engage the Chorus Phaser switch on the Synthesizer, and the effect thickens, with the Strings and Synth outputs summed and processed together. It’s not subtle, but it’s never harsh. Even at full depth, it retains clarity, never muddying the low end. This circuit is a big reason why the Omni 2 still sounds modern—because it doesn’t just add movement, it adds emotion.

Tri-Phonic Output: Three Synths in One Cabinet

Few synths of the late ’70s offered separate outputs for distinct sound sections, but the Omni 2 did—and it mattered. The Strings, Synthesizer, and Bass each have their own dedicated output on the back panel, allowing for independent amplification and effects processing. Run the Bass through a tube preamp, send the Strings to a plate reverb, and route the Synthesizer through a phaser, and you’ve essentially got three instruments in one. ARP called this “Tri-phonic” operation, and while the term didn’t catch on, the concept did. It’s a workflow that anticipates modern DAW routing, letting players shape each layer independently. In an age when most synths had a single output and players relied on studio effects, this was a quiet revolution.

Hollow Waveform and Staccato Switch: Subtle but Effective Tweaks

The Omni 2’s front panel looks simple, but the details matter. The “Hollow Waveform” switch—renamed from the Omni’s “Waveform Enhancement”—engages a square wave in the Synthesizer section, giving leads and pads a hollower, more nasal character that cuts through a mix without becoming shrill. It’s not a second oscillator, but it’s a useful timbral shift. Then there’s the Staccato switch, which alters the Bass section’s envelope decay for tighter, punchier lines. It’s a small touch, but one that makes the Omni 2 more expressive than its preset nature might suggest. These aren’t deep synthesis tools, but they’re thoughtful refinements that give players real-time control over articulation.

Historical Context

The Omni 2 arrived in 1978, right as the synth world was pivoting from preset organs to programmable polysynths. Sequential Circuits had just released the Prophet-5, a fully programmable, microprocessor-controlled synth with dynamic voice allocation—something the Omni 2 could never match. But the Prophet-5 cost nearly twice as much, and most players weren’t ready to dive into patch programming. The Omni 2 filled a sweet spot: it offered polyphony, analog warmth, and instant access to professional sounds without requiring a computer science degree.

ARP positioned it as a stage and studio workhorse—something a keyboardist could wheel in, plug in, and play. It wasn’t trying to be a lead synth or a sound design lab. It was a texture machine, built for pads, strings, and bass. And it sold. While exact numbers are elusive, some sources suggest the Omni series was briefly the best-selling synth in the world during its peak. Bands like The Cars, Journey, and Modern English used it heavily, not because it was cutting-edge, but because it was reliable. It stayed in tune, it powered up quickly, and it sounded great on a two-track demo.

It also arrived at the tail end of the string machine era. By 1981, digital synths and samplers were on the horizon. The Omni 2 was one of the last major analog string synths released before the market shifted. Its all-steel chassis and robust construction reflect that transitional moment—ARP building a tank for a world that was about to go digital.

Collectibility & Value

Today, the Omni 2 trades in a narrow but passionate market. Working units in good condition typically sell for $2,200 to $3,000, with pristine examples hitting $3,500. Non-working units go for $800 to $1,500, depending on completeness and case condition. Given its 70-pound weight and complexity, shipping is a major factor—many buyers prefer local pickup.

The biggest threat to longevity? Capacitors. The Omni 2’s power supply and audio path rely on electrolytic capacitors that degrade over time. Owners report failing power supplies, hum, and intermittent operation—all common symptoms of capacitor decay. A full recapping is strongly recommended for any unit that hasn’t been serviced in the last 15 years. Service technicians observe that the keyboard bushings also wear out, leading to sticky or unresponsive keys. Re-bushing is a known fix, but it’s labor-intensive.

Another issue: the bus-bar keyboard system. Unlike modern synths with individual key contacts, the Omni 2 uses a shared voltage rail that can develop resistance or corrosion. This leads to “ghost notes” or dead keys, especially in the mid-register. Cleaning the contacts helps, but full restoration often requires disassembly and re-lubrication.

MIDI retrofits are possible but non-trivial. The dual bus-bar system and negative voltage triggering complicate standard MIDI-to-CV solutions. Successful mods, like the Doepfer MTC-64 with opto-isolators, exist but require advanced soldering skills. Factory-original units without MIDI are more desirable to purists, but players who want integration often budget for a professional retrofit.

When buying, check:

- All three outputs for noise or imbalance

- Chorus Phaser operation (listen for dropout or uneven sweep)

- Keyboard responsiveness across all 49 keys

- Power supply stability (no hum, no voltage sag)

- Case integrity (the steel chassis can dent, but structural damage affects grounding)

It’s not a synth for beginners, but for players who value character over convenience, the Omni 2 remains a compelling choice. It won’t do everything, but what it does, it does with soul.