Sequential Circuits Pro-One (1981–1984)
A no-nonsense, feature-packed monosynth that brought professional analog synthesis within reach of bedroom studios and touring musicians alike.
Overview
The Sequential Circuits Pro-One isn’t just a synth—it’s a statement. Released in 1981, it arrived at a pivotal moment when analog synthesis was being squeezed by the promise of digital novelty, yet demand for warm, hands-on sound remained strong. Priced at a shockingly accessible $795, the Pro-One offered a level of sonic sophistication and real-time control that belied its cost. With two voltage-controlled oscillators, a Curtis filter chip that snarled like a cornered panther, and a fully programmable 16-step sequencer built right in, this was no toy. It was a working musician’s weapon: compact enough for a flight case, powerful enough to cut through a mix, and intuitive enough to inspire at 3 a.m.
Players ranged from underground synth-poppers to session players needing a quick bassline fix. The Pro-One carved out a niche as the thinking person's monosynth. No wood panels, no flashy lights. The mini-keyboard has 37 keys, no velocity, and pitch and mod wheels, and it felt surprisingly responsive. The layout was so logical that you could dive in without touching the manual. Most owners read it anyway. Vince Clarke (of Depeche Mode and Yazoo fame) reportedly used it alongside his Sequential Circuits Pro-1, and its bass tones have underpinned tracks across new wave, industrial, and early electronic dance music.
Specifications
| Oscillators | 2 VCOs with sawtooth, triangle, square, pulse, and noise waveforms |
| Filter | 1 VCF (24dB/oct low-pass, 12dB/oct band-pass, 6dB/oct high-pass) with resonance |
| Envelope Generators | 2 ADSR (attack, decay, sustain, release) generators |
| LFO | 1 LFO with triangle, square, and sample-and-hold waveforms |
| Keyboard | 37-note mini-keyboard with pitch bend and modulation wheels |
| Sequencer | 16-step built-in sequencer with memory for 128 sequences |
| Arpeggiator | Up, down, up/down, and random modes |
| Audio Outputs | 1x 1/4" unbalanced (150 ohms output impedance) |
| Audio Input | 1x 1/4" external audio input for filter processing |
| Control Voltage | CV/Gate, S-Trig, and Sync inputs/outputs |
| Power | 100–120 VAC, 60 Hz, 20 watts |
| Dimensions | 35.5" x 11.5" x 4.25" (90.2 x 29.2 x 10.8 cm) |
| Weight | 17 lbs (7.7 kg) |
| Patch Memory | 16 user-programmable memory locations |
| Country of Manufacture | United States |
| Original MSRP | $795 (1981) |
| Years Produced | 1981–1984 |
Key Features
- Built-in 16-step sequencer with 128 sequence memory: This wasn’t just a novelty—it was a full compositional tool. You could chain sequences, sync them to external gear via CV, and store complex patterns that would otherwise require a separate box. In 1981, having this kind of sequencing power built into a $795 synth was borderline revolutionary.
- CV/Gate and S-Trig compatibility: The Pro-One didn’t live in a bubble. With full CV/Gate and S-Trig I/O, it played beautifully with modular systems and drum machines of the era. Want to sync your Moog Rogue to your Roland TR-808? Route the Pro-One as the master clock. It was a bridge between worlds.
- External audio input for filter processing: Feed in a guitar, a drum machine, or even a cassette deck—the Pro-One’s Curtis filter would mangle it with glorious analog warmth. This feature turned it into a sound design tool, not just a synth.
- 16 user-programmable patch memories: At a time when many synths were entirely non-programmable (looking at you, Moog Rogue), being able to save and recall 16 sounds was a godsend for live use. No more tweaking knobs between songs.
- True analog arpeggiator with random mode: The arpeggiator wasn’t an afterthought. With up, down, up/down, and—rare for the time—random modes, it could generate unpredictable, evolving patterns that felt almost alive. Try random mode with a high resonance setting and a slow LFO on filter cutoff. You’ll thank me later.
Historical Context
The Pro-One followed the Sequential Circuits Pro-1 (1979-1981), a simpler, non-programmable monosynth. The Pro-One added features, memory and connectivity. It arrived just as the Prophet-5 was redefining polyphony. The Pro-One was monophonic, but it was affordable and immediate. The Prophet-5 cost over $5,000, and the Pro-One was under $800. That made it one of the first professional-grade synths a gigging musician could justify buying without a record deal.
Its main competitor was the Moog Rogue, released the same year. The Rogue had a simpler architecture (one VCO, no sequencer, no patch memory). It had that legendary Moog filter, but it lacked the Pro-One's versatility. The Pro-One was the engineer's choice; the Rogue, the purist's. The Pro-One's design carried on in the Sequential Circuits Six-Trak (1984), a six-voice paraphonic synth that expanded on the Pro-One's programmability and multitimbrality.
Collectibility & Value
Today the Pro-One is considered uncommon but not rare. Roughly 3,000 units were reportedly produced across both Mk I and Mk II versions. Its desirability is high, especially among synth enthusiasts who value hands-on control and real sequencing power without the bulk of a modular rig. As of 2025, a fully functional Pro-One in good condition sells for $1,200 to $2,000 USD. Mk II models (black panel, gold labels) often command a slight premium due to their improved circuit stability.
These machines are over 40 years old. The most common issues are capacitor degradation in the power supply, which can lead to hum, noise, or even failure, and wear on the mini-keyboard contacts, which causes note dropouts. A Pro-One that hasn't been serviced in decades is a project, not a purchase. When buying, insist on a unit that powers on cleanly, sequences reliably, and has full keyboard response. The original manual is a detailed 40-page guide, and it's a bonus if included. A unit with the original foam padding intact inside the case is a rare find.
Market Value
┌──────────────────────────────────────────────────────────────────────────┐ │ SEQUENTIAL CIRCUITS PRO-ONE Apr 2026 │ ├──────────────────────────────────────────────────────────────────────────┤ │ High $971 Latest $971 │ │ Median $47 Trend ▲ Up │ │ Low $42 Volume ~3/mo │ ├──────────────────────────────────────────────────────────────────────────┤ │ $1,000 ┤ │ │ │ .│ │ │ │ │ $571 ┤ │ │ │ │ │ │ │ │ │ │ │ $0 ┤. . │ │ ├─────────────────────────────────────────────────────────────────│ │ vol │█ █ █│ │ └─────────────────────────────────────────────────────────────────│ │ 2026-02 2026-02 2026-03│ └──────────────────────────────────────────────────────────────────────────┘
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