ARP Omni II (1978–1981)

The ARP Omni II doesn’t whisper vintage charm—it announces itself with a wall of shimmering strings and a bass growl that cuts through any mix, like a time machine set to 1979.

Overview

Plug in the Omni II, flip the power switch, and within seconds you’re enveloped in that signature ARP chorus—a slow, liquid swirl that feels like warm oil poured over glass. It’s not just a string machine; it’s a mood generator. The moment you hit a chord, the strings bloom with that unmistakable analog thickness, layered with a phaser so integral to the sound it might as well be baked into the circuit board. But what really sets the Omni II apart is how it layers roles: it’s a string ensemble, a paraphonic synth, and a monophonic bass machine, all living under one heavy steel chassis. You can stack the string section with the synth for a richer pad, then drop a fat, filter-swept bassline underneath—all at once, all in real time. That kind of multitasking was rare in 1978, and it made the Omni II a secret weapon in studios from LA to Manchester.

Compared to its predecessor, the Omni II tightened up the act. The original Omni (1975–1977) was groundbreaking but clunky—mechanical switches, limited envelope control, and a slightly brittle tone. The II replaced those with all-electronic switching, which not only made the interface faster and more reliable but also eliminated the mechanical chatter that plagued early units. More importantly, it introduced a full ADSR envelope for the synth section, giving players actual shaping power over their sounds. Before this, you were stuck with simple AR (attack-release) contours. Now, you could dial in a snappy pluck, a swelling pad, or a sustained lead with real precision. The bass section got its own dedicated output and a preset ADR envelope, making it easy to route to a separate amp or mixer channel—ARP called this “Tri-phonic” output, and it was a godsend for live players who wanted to keep the bass tight and punchy without muddying the strings.

The synth section itself is deceptively simple: one oscillator per voice (derived from divide-down logic, not true VCOs), a 24dB/oct low-pass filter, and an LFO that modulates the VCF. But that filter—ah, that filter. It’s the same smooth, singing four-pole design found in the ARP 2600 and Odyssey, and it gives the Omni II a warmth that rivals any polysynth of its era. It doesn’t scream like a Minimoog, but it doesn’t need to. This is a synth that breathes, that swells, that feels alive when you tweak the cutoff. And while the strings are preset, the synth section is fully tweakable—attack, decay, sustain, release, filter cutoff, resonance, LFO rate, and depth. You won’t find oscillators with multiple waveforms or FM capabilities here, but you don’t need them. The Omni II excels at texture, not complexity.

And then there’s the Hollow Waveform switch—a rebranded version of the Omni I’s Waveform Enhancement. Flick it on, and the synth’s default quasi-sawtooth wave shifts to a square wave, thinning out the tone and giving it a hollower, more nasal character. It’s not a dramatic change, but it’s useful—great for adding edge to a pad or cutting through a dense mix. It’s also the secret sauce behind the lead in Modern English’s “I Melt With You,” that icy, pulsing line that floats above the chorus like a ghost.

Specifications

Key Features

Tri-Phonic Output Architecture

The Omni II’s three separate outputs—Strings, Synthesizer, and Bass—weren’t just a convenience; they were a performance philosophy. By splitting the signal paths, ARP let players treat each section like a separate instrument. Run the strings through a spring reverb, the synth through a phaser, and the bass into a clean DI box—suddenly, you’re not just playing a synth, you’re conducting a small orchestra. This setup was especially powerful in live settings, where stage volume and monitor mixes could easily turn a dense synth into a muddy mess. With individual outs, the Omni II stayed articulate, even in loud environments. And in the studio, engineers loved it: no need to commit to a mix upfront. You could record each section dry and process them independently, giving producers the kind of flexibility that was rare in pre-MIDI gear.

All-Electronic Switching

Gone are the mechanical relays of the Omni I, replaced by solid-state switching that’s faster, quieter, and more reliable. This wasn’t just a reliability upgrade—it changed how the synth felt under your fingers. No more clunking between modes, no more missed notes from slow relay response. The transition between string and synth voicings became seamless, and the Single/Multiple Trigger option gave players real expressive control. Set to Single, the envelope triggers only on the first note pressed—perfect for legato lines. Set to Multiple, every note gets its own envelope hit, ideal for rhythmic, staccato playing. It’s a subtle but powerful performance feature that made the Omni II more dynamic than its preset-heavy appearance suggested.

ARP’s Legendary Chorus/Phaser

The heart of the Omni II’s magic lives in its 3-voice chorus/phaser circuit—a patented ARP design that’s as essential to the sound as the filter itself. It’s not just a chorus; it’s a slow, modulating swirl that gives the strings their signature motion. Engage it on the synth section, and the whole character shifts: the attack softens, the tone thickens, and the LFO slows down, creating a dreamier, more ambient texture. This isn’t an effect you add later—it’s baked into the instrument’s DNA. And unlike many string machines of the era, which used simple BBD-based delays, the Omni II’s circuit is more complex, with multiple modulation stages that create a richer, more organic movement. It’s the reason why the Omni II never sounds static, never sounds like a recording—it always feels alive.

Historical Context

The late 1970s were a transitional moment in electronic music. The era of the monosynth was fading, and musicians were hungry for polyphony—real, playable chords. But true polyphonic synths like the Sequential Circuits Prophet-5 were still years away from mass adoption, and they were prohibitively expensive. String machines filled the gap, offering lush, orchestral textures at a fraction of the cost. The Solina String Ensemble led the charge, but ARP saw an opportunity to do more. They didn’t just want to clone the Solina—they wanted to build something that could do strings *and* synthesis, that could be both accompaniment and lead instrument.

The Omni II arrived in 1978, right as new wave and post-punk were taking shape. Bands like The Cars, Joy Division, and Modern English weren’t looking for symphonic realism—they wanted atmosphere, texture, mood. The Omni II delivered. Its strings weren’t trying to fool anyone into thinking they were real violins; they were something else entirely—synthetic, shimmering, slightly alien. That’s why it showed up on “Moving in Stereo,” why it haunts the low end of “Don’t Stop Believin’,” why it underpins the icy melancholy of Joy Division’s *Closer*. It wasn’t a background instrument; it was a character in the story.

And while ARP was known for its high-end synths like the 2600 and Odyssey, the Omni series was their commercial breakthrough. Some sources claim it was the best-selling synth of its time, a claim that’s hard to verify but feels plausible given how widely it was used. It wasn’t the most advanced synth on the market, but it was one of the most practical. For gigging musicians, it was portable, durable, and road-ready. For studio players, it was a one-stop shop for pads, textures, and bass. And for bands on a budget, it was a way to sound huge without hiring an orchestra.

Collectibility & Value

Today, the ARP Omni II is a sought-after piece, but it’s not a stratospheric collector’s item like a rare Prophet or a mint Minimoog. Prices typically range from $1,600 to $2,500, depending on condition and service history. Fully serviced units with recap’d power supplies and cleaned sliders can fetch over $3,000, especially if they come with the original case. But be careful: many Omnis on the market are sold “as-is,” and that can be a minefield.

The biggest enemy of the Omni II is time. Electrolytic capacitors degrade, and when they fail, they can take other components with them. The power supply is particularly vulnerable—old capacitors can leak, corrode traces, and cause voltage instability. A unit that powers on but sounds thin or noisy is likely in need of a full recap. Service technicians observe that a proper recapping job can cost $400–$600, but it’s often worth it. Beyond the power supply, the sliders and switches need attention. Sliders can get scratchy, and the optical encoder in the keyboard (used for note detection) can fail, causing notes to drop out or stick. Rebushing the keys is a common fix, and while it’s labor-intensive, it restores the playability that makes the Omni II so satisfying to use.

Another issue is the Hollow Waveform switch. It’s a simple toggle, but over time the contacts can oxidize, leading to intermittent operation. Some owners report that the switch needs cleaning or replacement after decades of use. And while the chassis is solid steel and holds up well, the faceplate can chip, and the orange and black paint scheme is prone to fading if exposed to sunlight.

For buyers, the advice is clear: don’t buy untested. Look for units with recent service records, clean sliders, and responsive keys. If the seller can provide audio demos, listen for even note response across the keyboard and a smooth, consistent chorus effect. Avoid units with visible corrosion, burnt smells, or flickering power LEDs. And if you’re not planning to service it yourself, factor in the cost of professional restoration—it’s not a “plug-and-play” vintage synth unless it’s already been gone through.

Despite its quirks, the Omni II holds its value well. It’s not just nostalgia; it’s a genuinely useful instrument. The string sound is still unmatched in its class, and the synth section holds its own against modern plugins. And with free emulations like Full Bucket Music’s Oxid, more people are discovering the Omni II’s sound than ever before—driving interest in the real thing.

eBay Listings

As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.

Related Models

• ARP Omni 1
• ARP Omni 2
• 4ms Ping
• ADC 27
• 2hp LPG V2
• ALM AXON-2
• AMS DMX 2000
• Marantz SD-930
• Accuphase A-60
• Accuphase AC-1