ARP String Synthesizer (1974–1981)

The lush, beating hum of a hundred strings swells from a single keyboard — not quite real, not quite synth, but utterly hypnotic.

Overview

Plug in the ARP String Synthesizer, hit a chord, and it’s like someone opened a window to a 1970s recording studio at 3 a.m., when the tape was still rolling and the room was thick with reverb and possibility. That rich, chorused string pad that floats beneath so many classic tracks — from Jean-Michel Jarre to ELO to Herbie Hancock’s quieter moments — often came from this unassuming machine. But here’s the twist: the “ARP String Synthesizer” isn’t exactly what you think. It’s not a standalone ARP design in the way the Odyssey or 2600 were. Instead, it’s a hybrid — a marriage of the Solina String Ensemble, made by Eminent in the Netherlands, and ARP’s own Explorer synthesizer section, grafted on top. ARP didn’t build the string engine; they rebadged and enhanced it, adding their own synth voice, filter, and keyboard, then slapped their name on the front. That’s why you’ll see it called the ARP Solina, ARP String Ensemble, or just “that big brown keyboard with the fake wood,” depending on who you ask.

Despite its Frankensteined origins, the ARP String Synthesizer carved out a sound so distinct it became a genre unto itself. The string section uses divide-down oscillator technology — the same kind found in electronic organs — meaning every key shares a single top-octave generator, with dividers creating the lower notes. That’s not polyphony in the modern sense; it’s more like a carefully tuned illusion. But when you add the built-in analog chorus — a lush, slow, undulating circuit that modulates the signal across multiple delay lines — the result is a shimmering, three-dimensional pad that no digital plugin has fully replicated. It doesn’t just play chords; it breathes. And the synth section? That’s pure ARP: a duophonic analog voice with two oscillators, a 24dB/octave filter, and all the punch you’d expect from the same engineers who built the Odyssey. You can layer it with the strings for a hybrid lead, or use it independently for basslines and solos. It’s not the most flexible synth on the block, but it does what it does with a kind of warm, slightly unstable charm that feels alive.

Positioned between the budget-friendly Axxe and the flagship Quadra in ARP’s lineup, the String Synthesizer was never the company’s technical crown jewel. But it was a commercial workhorse — a “musician’s keyboard” for session players who needed instant, broadcast-ready textures without patching cables or tuning oscillators mid-song. It wasn’t for sonic experimenters; it was for pros who showed up, played, and got paid. And unlike the notoriously unstable early Moogs, ARP’s oscillator design meant this thing stayed in tune, even in the sweaty back of a tour van. That reliability, combined with its rich sound, made it a favorite in both studio and stage rigs throughout the late ’70s.

Specifications

Key Features

The Chorus That Changed Everything

The heart of the ARP String Synthesizer’s magic isn’t in its oscillators or filters — it’s in the chorus. While many string machines of the era used simple vibrato or detune, the Solina-derived section here employs a complex, multi-stage analog delay network that creates a slow, organic modulation across the stereo field. It’s not just a wobble; it’s a slow, swelling wave that mimics the natural pitch variations of a real string section. This circuit is why the ARP String sounds so alive compared to, say, the flat, static pads of the Korg Lambda or the Yamaha SS-30. It’s also notoriously fragile — the bucket-brigade devices (BBDs) that create the delay degrade over time, and the supporting capacitors dry out, leading to noise, dropouts, or complete failure. A well-recapped and serviced unit sounds like heaven; a neglected one can sound like a dial-up modem fighting for signal.

Duophonic Synth Meets String Machine

What sets this apart from other string synths of the era — like the Elka String Machine or the Roland RS-202 — is the inclusion of a full ARP analog synth voice. It’s not an afterthought; it’s a legitimate duophonic section with oscillator sync, ring modulation, and the same 24dB filter found in the Odyssey. You can play it alone, layer it with the strings, or use the keyboard’s split function to play synth in one hand and strings in the other. That flexibility made it a favorite for keyboardists who needed multiple textures in a single set. But it’s not a full-featured synth: no velocity, no aftertouch, and only basic envelope controls. Still, for live use, it was a game-changer — one keyboard, two distinct sonic personalities.

Arpeggiator With Character

The built-in arpeggiator is simple by modern standards — monophonic, with basic direction controls — but it has a distinct analog flavor. Unlike the rigid, quantized arpeggios of later digital synths, this one has a slight waver in timing and pitch, giving it a human, almost nervous energy. It works best with the synth section, creating pulsing sequences that feel urgent rather than mechanical. It’s not programmable, and it can’t sync to external clock (no MIDI, remember), but in a world of manual tape loops and clunky sequencers, having an arpeggiator built into your main keyboard was a serious advantage.

Historical Context

The ARP String Synthesizer arrived in 1974, right as the demand for polyphonic textures was exploding. The Minimoog ruled the solo sounds, but it was monophonic — useless for pads. The Polymoog and Yamaha CS-80 were on the horizon, but they were prohibitively expensive and notoriously unreliable. Enter the string machine: a relatively affordable, fully polyphonic keyboard that could deliver instant orchestral textures. Eminent’s String Ensemble was already a hit in Europe, and ARP saw an opportunity. By combining it with their own synth section, they created a hybrid instrument that appealed to both pop session players and progressive rock keyboardists who wanted more than just strings.

At the time, ARP was riding high — outselling Moog and dominating the synth market with the Odyssey, 2600, and Omni. The String Synthesizer wasn’t a technical breakthrough, but it was a smart product: it leveraged existing technology to fill a gap in the lineup. Competitors like Roland and Korg would soon follow with their own string/synth combos, but the ARP version stood out for its superior tuning stability and that unmistakable chorus. It became a staple in genres from disco to jazz fusion, heard on records by ABBA, Parliament-Funkadelic, and Vangelis. But by the late ’70s, the writing was on the wall. The rise of digital synthesis, the failure of the Avatar guitar synth, and internal mismanagement led to ARP’s bankruptcy in 1981. The String Synthesizer faded with the company, but its sound lived on — sampled, emulated, and revered.

Collectibility & Value

Today, the ARP String Synthesizer trades in a narrow but passionate market. Units in excellent condition with a fully functional chorus and synth section fetch between $3,500 and $5,000, depending on provenance and mods. Cosmetic condition matters — the fake woodgrain peels easily, and the brown vinyl corners tear, so a clean cabinet can add $500 or more to the value. But the real cost isn’t the purchase price; it’s the restoration. Most units on the market need at least a recap — replacing the electrolytic capacitors in the power supply and audio path — which can run $600 to $1,000. The BBD chips in the chorus are often degraded, and replacements are scarce. Some technicians retrofit modern equivalents, but purists argue it changes the character.

Common failures include failing key contacts (leading to dead notes), cracked solder joints on the heavy transformer, and failing membrane switches in the control panel. The arpeggiator is prone to timing drift, and the headphone amp often cuts out. Before buying, insist on a full demo — listen for noise, dropouts, and tuning instability. Check that the chorus engages cleanly and that the synth section tracks across the keyboard. Avoid units that smell of burnt electronics or have visible corrosion on the circuit boards.

Despite its quirks, it’s not a “museum piece.” It’s a playable, expressive instrument that still sounds unlike anything else. For the right player — someone who values vibe over versatility — it’s worth the hassle. But it’s not for beginners. This is a machine that demands maintenance, patience, and a tolerance for vintage fragility. Own one, and you’re not just buying a synth; you’re adopting a project.

eBay Listings

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