Instruments: JPS Harmonic Synthesizer


JPS Harmonic Synthesizer



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With an all-analog audio path, and rock-solid digital harmonic oscillators, the RMI Harmonic Synthesizer was the world's first digital synthesizer.

JPS Harmonic Synthesizer (Front View)

With an all-analog audio path, and rock-solid digital harmonic oscillators, the RMI Harmonic Synthesizer was the world's first digital synthesizer. Produced in very limited quantities for a very short period in the mid-1970s, at long last here is your opportunity to own a loving recreation of this beautiful, and exceptionally ultra-rare, classic American synthesizer.

Best known for its prominent role in Oxygéne, where it was used extensively (and usually through an Electric Mistress flanger) for basses (Parts II and IV), leads (Parts IV and V) and sequences (Part V), the RMI was almost a decade ahead of its time.

With surprisingly deep but clean and harmonically rich basses and cutting leads, this restored version improves on the original by adding extra features such as a 4-stage envelope and polyphony, it's slightly lo-fi waveform will add a unique character and texture to your tracks.

The JPS Harmonic Synthesizer faithfully models the original schematics of the legendary RMI Harmonic Synthesizer, adding some new tricks to fill in the gaps of, and vastly extend, the original feature set. We also include an original Acidman FX Array for quick effects programming, including the all-important flanger, and a chorus based on our Chenille Chorus Ensemble.

Sixteen harmonics may not sound like very many compared to later additive hardware and soft-synths which offer 256 partials or more, but unlike those devices, the harmonics on the Harmonic Synthesizer are not pure sines: each "harmonic" was actually quite rich in other harmonics. So what looks like a limitation actually offers its own benefits—lots of harmonics but with easy programming and tweaking, making using the instrument simplicity itself to create dirty saws, all of which contributes to the raw, slightly lo-fi and truly vintage sound.

In addition, the Harmonic Synthesizer included four preset harmonic tones. In the original instrument there were 4 presets on Oscillator 1, and 3 on Oscillator 2, plus a dedicated Pulse wave generator per oscillator. What is interesting in the schematics is that it appears there was space in the design for an additional preset on each oscillator. So for the JPS we've invented an extra preset per oscillator! You now also have "Strings" on Oscillator 1 and "Complex" on Oscillator 2, both offering more saw-like tones with an improved low end from that available via the original Reed preset alone.

And despite the fact the oscillators are digital, the machine sounds surprisingly warm and analog once you push its filters to reduce the natural brightness, while retaining the ability for it to cut cleanly through your mix, in that special way additive synthesis can achieve.

The JPS Harmonic Synthesizer

Two oscillators

  • Classic RMI Digital Harmonic Generators with an all-analog audio path
  • Modeled logarithmic, resistive potentiometers
  • 16 harmonic level faders per oscillator allow precise harmonic adjustment
  • New Shape fader allows the waveform to be adjusted from the bit-limited, rectified RMI default to a sine
  • Additionally, the original design of 5-bit generators can be adjusted down to 4-bit for an even more lo-fi tone, or up to 8-bits to provide a pure (or at least, an 80's era) sine when minimizing the Shape control
  • Full analog ADSR envelope generator, with adjustable curves
  • Note Off triggering option for Oscillator 2 allows you to play the note with an AHD envelope after it has been released!
  • Oscillator Filter, Octave Select and Tuning, and Volume level
  • Oscillator 1 can now directly Ring Modulate Oscillator 2
  • Independent oscillator panning
  • Mono Retrigger, Mono Legato, and Polyphonic voicing options. (Up to 64 voices can be set, but we recommend 6-12 voices)
  • Up to 8x oversampling removes aliasing

Multiple Presets

  • Use the harmonic generators directly by adjusting the harmonic faders, or via presets. Multiple presets can be used simultaneously
  • Modeled parallel resistor network
  • Oscillator 1 features a Pulse generator, the four original RMI presets, plus a new and exclusive preset, "Strings"
  • Oscillator 2 can be Synced to Oscillator 1, and you can select from a Pulse generator, three original RMI presets, plus another new and exclusive preset, "Complex"

Tremulant Modulation

  • Separately adjustable vibrato and tremolo
  • Syncable or free-running, mono or polyphonic LFO
  • While we've kept the original single-LFO of the original keyboard, additional CV LFO inputs can be used to over-ride the internal LFO to those targets. Combinator presets for Malstrom LFO output and a selection of third-party LFO devices are included

Automatic Sequencer/Arpeggiator

  • Both of the RMI sequencer modes, "Up" and "Random", are available, and for the JPS can be free-running or synced, with key hold (which in the original keyboard was obtained by literally shoving wooden sticks above the keys and into the case to hold them down!) and we've also added a polyphonic gated mode!

Noise Modulation

  • Colour-adjustable noise generator (pink to white) which can be used to frequency modulate the oscillators for a wide range of classic noise effects like percussion, traps, wind and thunder

Dynamic Filter

  • The RMI Filter is modeled using an advanced Zero-Delay Feedback analog filter, and supplies mixable Low-, Band- and High-Pass outputs
  • Q/Resonance amount
  • A Filter Frequency control has been added for more precise operation
  • Sinusoidal LFO modulation (with external LFO over-ride option)
  • Up/Down envelope sweep, with adjustable curve
  • Oscillator 2 can be internally routed to the filter
  • The original monophonic external audio input into the filter on the Oscillator 1 channel is also available


  • The RMI features both portamento and an attack-envelope shaped pitch-bend with adjustable curve
  • The JPS adds a pitch-wheel with a dual-direction range setting on each oscillator for complex and unique pitch-bend range programming; send Osc 1 pitch UP and Osc 2 pitch DOWN with just a pitch wheel up movement!

Everything Automation­™! (CV Galore!)

  • All front panel controls can be automated via sequencer and Remote™, and there is a CV input for all the Harmonic Synthesizer controls, including dedicated LFO inputs to over-ride the internal LFO to the five internal LFO targets

JPS Harmonic Synthesizer (Back View)

Extensive Patches

  • 799 Harmonic Synthesizer patches, including over 200 Signature presets by some of Reason's leading patch-makers
  • 52 Reason-only Combinators
  • 46 Modular RE Combinators
  • 5 TMA Tutorial Combinators. Grab the free TMA Commentator series here

An Authentically 1970s Harmonic Synthesizer User ManualDownload User Guide

  • You didn't grab it above already?! Then pick it up now via this link instead!

Acidman FX Array

The Acidman FX Array is pre-connected and fixed to the JPS Harmonic Synthesizer by RCA/phono jacks, instantly giving you six exciting, classic stomp box setups. A pair of standard quarter-inch stereo input jacks allow you to easily attach external synths or effects through Acidman. (Please note that the JPS Harmonic Synthesizer's "Master Output" control is post-Acidman.)

Acidman FX Array (Front View)

  • Band-selectable Distortion
  • Chorus/Ensemble, based on the Chenille Chorus Ensemble Rack Extension
  • Classic BBD-style Flanger
  • 5-stage Phaser
  • Stereo Delay
  • Vintage Reverb