ARP Omni-2 (1978–1981)

Name: ARP Omni-2
Brand: ARP

The moment you hit a chord and that chorus kicks in, it’s like being wrapped in a warm, wobbly blanket of 1970s analog soul—thick, slightly unstable, and utterly hypnotic.

Overview

Turn on an ARP Omni-2 and let a slow major seventh chord hang in the air, drenched in its three-voice chorus phaser, and you’re instantly transported to the backline of a 1979 arena tour—somewhere between Tangerine Dream’s fog-drenched synthscapes and The Cars’ icy new wave precision. This isn’t a synthesizer for surgical sound design or hyper-expressive leads. It’s a mood machine, a polyphonic engine built to fill rooms with lush, undulating string pads and a synth section that, while modest, cuts through with a polite but present analog sheen. The Omni-2 doesn’t ask to be the center of attention; it’s happiest weaving in the background, thickening arrangements with its signature wobble, letting the bass section growl underneath in monophonic dignity.

Compared to the explosion of fully programmable polysynths that followed—Prophet-5, Jupiter-8, even ARP’s own Quadra—the Omni-2 feels like a transitional artifact, a bridge between the preset-driven world of string machines and the coming era of dynamic voice allocation. It uses divide-down oscillator architecture, the same top-octave generator tech found in home organs, meaning every note on the 49-key keyboard shares a single oscillator source per section. That’s why it’s technically paraphonic: all notes in a chord pass through the same filter and amplifier envelope, so playing complex voicings results in a slight mushiness, a softening of attack and resonance. But that’s also its charm. Where a Prophet-5 gives you precision, the Omni-2 gives you atmosphere—imperfect, slightly detuned, and alive in a way that feels more like a real ensemble than a machine.

The Omni-2 was ARP’s refinement of the original 1975 Omni, and it shows in the details. The chassis is all steel, painted in ARP’s bold orange and black scheme that screams late ’70s synth credibility. It’s heavy—33 pounds of industrial build quality that says this thing was meant to tour. And unlike the original, which had a somewhat flimsy case and basic triggering, the Omni-2 introduced selectable single or multiple triggering, giving players more control over envelope behavior. Want each note to retrigger the filter and amp envelope cleanly? Flip it to single. Prefer that vintage, smeared organ-style sustain where chords bleed into each other? Stick with multiple. It’s a small feature, but one that expands the instrument’s expressive range beyond mere background padding.

Specifications

Manufacturer	ARP Instruments, Inc.
Production Years	1978–1981
Original Price	$2,250
Keyboard	49 keys, non-weighted, organ-style
Polyphony	49 voices (divide-down architecture)
Timbrality	2 (Strings and Synthesizer sections)
Sections	Strings (polyphonic), Synthesizer (polyphonic), Bass (monophonic)
Oscillators	Top-octave generator with divide-down circuitry (Mostek MK50240)
Waveforms	Quasi-sawtooth (default), Square (via Hollow Waveform switch)
Filter	24dB/oct low-pass (Model 4075), shared across Synthesizer section
Filter Envelope	ADSR
Amplifier Envelope	ADSR (Omni-2), AR (Omni-1)
LFO	1 x sine wave for Strings; additional LFO for filter modulation on Synthesizer section
Effects	3-voice Chorus Phaser (patented ARP circuit)
Outputs	Separate 1/4" jacks for Strings, Synthesizer, and Bass (Tri-phonic output)
Inputs	Gate and Trigger In, VCF CV In, ADSR Release In
Weight	33 lbs (15 kg)
Dimensions	38.5" x 13.5" x 4.5" (97.8 x 34.3 x 11.4 cm)
Power	120V AC, 60 Hz (with internal power supply)
Memory	None (preset voicings only)

Key Features

The Chorus Phaser That Defined an Era

The Omni-2’s beating heart is its patented 3-voice Chorus Phaser—a circuit ARP claimed was superior to the original Omni’s and many competitors’. It wasn’t just a simple delay-based chorus; it used a complex phase-shifting network that created a rich, swirling motion, giving the string section its signature “underwater cathedral” quality. When engaged, it doesn’t just add movement—it transforms the entire character of the sound, turning static pads into living, breathing textures. The effect can be routed to both the Strings and Synthesizer sections simultaneously, though doing so slows the modulation rate slightly, creating a dreamier, more ambient wash. It’s this circuit that made the Omni a favorite in post-punk and new wave studios, where producers wanted that slightly melancholic, drifting pad beneath cold, detached vocals. Joy Division’s *Closer*, New Order’s early work, and The Cars’ debut all bear its watermark.

Tri-phonic Outputs: A Studio Engineer’s Dream

While most string machines of the era mixed everything internally, the Omni-2 offered separate 1/4" outputs for Strings, Synthesizer, and Bass—ARP called this “Tri-phonic” in their literature. This wasn’t just a gimmick; it gave engineers unprecedented control in the mix. You could send the strings to a plate reverb, the synth through a phaser, and the bass straight to a DI, treating each section like a separate instrument. In an age before digital workstations, this level of routing flexibility was rare and powerful. It also meant live players could split signals to different amps, creating stereo or even three-way spatial effects on stage. Few string synths offered this out of the box, and it’s one reason the Omni-2 remained in demand long after its production ended.

Hollow Waveform and Multiple Triggering

The Omni-2 replaced the original’s “Waveform Enhancement” switch with a more evocative “Hollow Waveform” control, which toggled the oscillator from a quasi-sawtooth to a square wave. The difference is subtle but useful: the default sawtooth gives warmth and body, while the square wave adds a nasal, reed-like character that cuts through dense mixes. It’s not a dramatic timbral shift, but it’s enough to give players a second flavor without complicating the interface. Equally important is the single/multiple triggering switch. On multiple, the envelope re-triggers only when all keys are released—a classic string machine behavior that creates smooth, legato swells. On single, each new note restarts the envelope, allowing for staccato articulation and more precise rhythmic playing. It’s a simple binary choice, but it dramatically expands the instrument’s usability beyond ambient pads.

Historical Context

When the Omni-2 arrived in 1978, the synth world was shifting. True polyphonic synths with programmable memory—like the Sequential Circuits Prophet-5—were beginning to emerge, offering dynamic voice allocation and patch storage. The Omni-2, by contrast, was a preset machine with no memory, no MIDI (it predated the standard), and a fixed architecture. Yet it sold well, reportedly becoming ARP’s best-selling instrument at one point. Why? Because for many working musicians, especially in rock and pop, the Omni-2 wasn’t competing with the Prophet-5—it was replacing the Mellotron, the Solina String Ensemble, and the need for session string players altogether.

The original Solina, with its Eminent 310 organ guts, had already proven that there was a market for portable string sounds. ARP took that concept and refined it—cleaner electronics, better build, and that superior chorus circuit. The Omni-2 wasn’t trying to be everything; it was trying to be the best at one thing: lush, analog, chorus-drenched ensemble textures. And in that niche, it succeeded. It arrived just as new wave and post-punk were taking off—genres that embraced synthetic textures but often on a budget. Bands didn’t need a full synth rig; they needed one box that could deliver strings, synth pads, and bass. The Omni-2 fit that role perfectly.

Its competitors were the Solina String Ensemble, the Elka Rhapsody, and the Crumar Performer—all using similar divide-down tech. But the Omni-2 stood out with its build quality, its tri-phonic outputs, and ARP’s reputation for reliability (relative to the era). It wasn’t cheaper—list price was $2,250, a serious investment—but for touring acts, its roadworthiness mattered. And while it never had the raw power of a Polymoog or the flexibility of a Prophet, it carved out a sonic identity that was unmistakable.

Collectibility & Value

Today, the ARP Omni-2 trades in a narrow but passionate market. Working units typically sell between $2,800 and $4,500, depending on condition, with pristine, fully serviced models sometimes fetching over $5,000. That’s a steep climb from the $200–$400 range of neglected, non-working units that still show up on eBay—often with “untested” listings that should set off alarm bells. The Omni-2 is not a synth to buy blind.

The biggest threat to longevity? Capacitors. Electrolytic capacitors in the power supply and audio path degrade over time, leading to hum, noise, or complete failure. Owners report that a full recapping—replacing all electrolytics—is often necessary, costing $400–$600 with labor. This isn’t optional maintenance; it’s essential for reliable operation. Beyond that, the keyboard is a known weak point. The organ-style keys are prone to wear, and bushings often dry out, causing sticking or uneven travel. Re-bushing the entire keyboard is a common restoration step, adding another $200–$300 to the tab.

Another issue: the original Omni-2 chorus phaser circuit relies on delicate analog components, including bucket-brigade devices (BBDs) and precision resistors. If the chorus sounds thin, staticky, or uneven, it’s likely the BBDs have failed or the supporting circuitry has drifted. Repairing this requires a technician familiar with vintage analog effects—not a common skill. And because ARP never released a full service manual, troubleshooting often relies on community-shared schematics and forum wisdom.

What to check before buying? First, power it on and listen. The chorus should engage with a smooth, wobbling sweep—no crackling, no dead channels. Test every key in the string section for dropouts; divide-down synths often have dead octaves if a counter chip fails. Check the individual outputs: do the strings, synth, and bass all come through cleanly? Is the filter sweep on the synth section smooth and resonant? If it’s stiff or scratchy, the potentiometers need cleaning or replacement. And verify the triggering behavior: switch between single and multiple modes and play staccato vs. legato phrases to confirm the envelopes respond correctly.

Despite the maintenance demands, well-kept Omni-2s are prized for their authenticity. Software emulations like GForce’s Virtual String Machine or Puremagnetik’s Kardoni come close, but they can’t replicate the subtle instability of aging analog circuits—the slight pitch wobble, the warm distortion of overdriven outputs. For producers chasing that 1979 studio sound, the real thing still matters.