ARP Omni (1975–1977)

That string pad behind "Moving in Stereo" or "Age of Consent"? Chances are it wasn't an orchestra. It was this box.

Overview

The ARP Omni was not the first string machine. It was ARP's first real attempt at the divide-down design, and it came out in 1977 with no patch cables and no modules, just a keyboard that promised an orchestra in a road case. It wasn't perfect and it wasn't clean, but the sound was distinct enough that it became the backbone of new wave, art rock, and studio pop before most players knew its name.

The Omni splits into three sections. There is a top-octave divide-down string section (polyphonic, chorused, and unapologetically artificial), a monophonic synthesizer section with filter, envelope, and oscillator controls, and a dedicated bass voice that is simple to the point of rudeness. It's not a full synth in the Odyssey sense. There's no oscillator sync, no noise source, and no LFO modulation routing. It's a hybrid, a compromise from a time when full polyphony meant $10,000 and a truck. At $2,250, the Omni was expensive for a preset machine, but it was a bargain next to a Polymoog. Unlike ARP's earlier String Ensemble (which was actually a rebadged Eminent 310), the Omni was all ARP - designed in-house, built in Massachusetts, and wrapped in a wood-paneled chassis.

The Omni gets its sound from the chorus cranked up and the strings swelling under a minor chord, and from a bass section that locks in with a drum machine. It's the machine behind The Cars' icy textures, Prince's early funk sketches, and Joy Division's cavernous atmospheres. It's not subtle and it doesn't do nuance. It does mood.

Specifications

Manufacturer	ARP Instruments, Inc.
Production Years	1975–1977
Original Price	$2,250
Polyphony	Full polyphony (strings/synth section), monophonic (bass)
Oscillators	Top-octave divide-down (strings), 1 VCO (synth section), 1 VCO (bass)
Waveforms	Violin, Viola (strings); Sawtooth, Square (synth and bass)
Filter Type	24dB/oct Low Pass Filter (synth and bass sections)
Envelope Generator	ADSR (synth section), ADR (bass section)
Chorus/Phaser	Built-in Chorus Phaser (strings and synth)
Keyboard	49 keys, non-weighted, split capable
Split Function	Yes, allows string/synth or string/bass split
Outputs	Stereo 1/4" jacks, XLR outputs
Inputs	Foot pedal (sustain, decay control), systems interface for ARP gear
MIDI	No
Power	115V AC, 60Hz (with internal power supply)
Weight	33 lbs (15 kg)
Dimensions	37" x 12" x 5"
Color Scheme	Wood paneling with silver faceplate (Mk I)

Key Features

The String Section: Artificial, But Addictive

The string engine is a top-octave divide-down oscillator. The design is borrowed from electronic organs, where a single high-frequency signal is divided electronically to produce all the lower notes. It isn't true analog synthesis, but it's efficient, and in the Omni it's colored by ARP's proprietary Chorus Phaser circuit. That circuit is more than a detune effect. It's a swirling, three-dimensional modulation that gives the strings their wobble and depth. Some string machines sound thin and brittle. The Omni's strings are thick, almost viscous, especially when layered with the synth section. The controls are minimal - just volume sliders for Violin and Viola.

Synth and Bass: Monophonic Muscle

The synth and bass sections handle the rest. The synth voice is a straightforward analog monosynth: one VCO with sawtooth and square waveforms, a 24dB/oct low-pass filter, and a full ADSR envelope. It's not as aggressive as the Odyssey, but it's warmer and more rounded, good for lead lines. The bass section is simpler still: a single oscillator, a fixed 2-pole filter, and an ADR envelope with a staccato switch that kills the decay for tight, punchy notes. It doesn't need effects. Under the strings it gives a full bottom end.

Split Keyboard and Integration

The keyboard can be split so the left hand plays strings while the right plays synth or bass. That suits one-man arrangements and live work. There's no programmable split point. It's fixed, around middle C. The systems interface on the back connects to other ARP gear like the 2600 or Axxe, so the Omni can act as a controller or sound source in a larger setup. It's not MIDI, but in 1976 it was forward-thinking.

Historical Context

The Omni arrived when synthesizers were still exotic, expensive, and mostly monophonic. Bands wanted strings, brass, and choirs, but session players were costly and organs couldn't deliver the same emotional weight. Divide-down technology gave full polyphony without individual oscillators per voice. Eminent had done it first with the Solina, and ARP had distributed their String Ensemble in the U.S. By 1975, ARP was ready to make its own version, one that integrated the strings with a real synth voice. The result was a self-contained keyboard that could do strings, leads, and bass without a patch cord in sight.

It wasn't alone. Competitors like the Polymoog and the Yamaha CS-80 offered true polyphonic synthesis, but at triple the price and twice the weight. The Omni became the "affordable" polyphonic synth - still pricey, but within reach of serious studio musicians and touring acts. It landed just as new wave and synth-pop were emerging. It appeared on records by The Cars, Joy Division, Prince, and Foreigner, often uncredited.

Collectibility & Value

A working ARP Omni is rare. Most units on the market are non-functional, and the power supply and tantalum capacitors are the notorious failure points. Owners report that nearly every Omni, regardless of condition, needs a full recap, especially on the power board and in the AR (Audio Research) capacitor arrays. After decades of dormancy, these old tantalums can leak, short, or even smoke when powered. Service technicians observe that restoration isn't optional. A proper rebuild can cost $400 - $600, depending on parts and labor, and it's not a job for beginners. The circuitry is dense, and the power supply runs high voltages.

A fully restored Omni is a prized unit. In excellent condition, with clean sliders, working chorus, and stable tuning, it can fetch $2,500 - $3,500. Units with original documentation, demo records, or factory service tags command premiums. Cosmetic condition matters. Chipped wood veneer or faded faceplate text can knock $500 off the value. Be wary of "tested working" claims on eBay; without a recent service history, assume it's on borrowed time. Ask for a video of the unit powering up and playing through all sections. If the strings sound thin or the bass cuts out, it's likely still suffering from capacitor issues.

The Mk I (1975-1977) is the original model, with wood panels and a silver faceplate. It's slightly rarer than the Omni-2, which followed in 1977 with an all-steel chassis, orange-and-black styling, and an improved chorus circuit. The Omni-2 is sturdier mechanically, but many purists prefer the Mk I's warmer, slightly looser sound.