Skip to content

JPS Harmonic Synthesizer v2

An iconic classic from the early 1970s, the legendary additive synthesizer from RMI, lovingly restored for your Reason rack.
JPS Harmonic Synthesizer v2 (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, its slightly lo-fi waveform will add a unique character and texture to your tracks.

Product Details

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.

Two Oscillators

  • Classic RMI Digital Harmonic Generators with an all-analog audio path
  • Modelled 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 16x oversampling to remove aliasing during rendering. (Please note increasing oversampling may alter the timbre of the noise generator function; in this scenario reduce the oversampling)

Multiple Presets

  • Use the harmonic generators directly by adjusting the harmonic faders, or via presets. Multiple presets can be used simultaneously
  • Modelled 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
  • New in version 2: Two additional internal LFOs are now available to control Osc 2 tremulance and Filter tremulance respectively

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 modelled 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 and internal LFO3 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. [except Over-sample and Binary Adder]

Extensive Patches

  • 799 Harmonic Synthesizer patches, including over 200 Signature presets by some of Reason’s leading patch-makers, including alteree, eXode, Navi, Odarmonix, and Weebl.
  • 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 Manual


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.

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

(Please note that the JPS Harmonic Synthesizer’s “Master Output” control is post-Acidman.)



  • Three alternative views: click the Circle/Square/Triangle View buttons at the top left of the Digital Harmonic Generators to select from:
    • Standard Harmonic Synthesizer: this view only includes the main Harmonic Synthesizer controls, but crucially it shows both DHG1 and DHG2 sliders in the same screen, for more easily adjustable side-by-side harmonic comparison and editing
    • +Extended Control Panel: single DHG edit, switch-able between DHG1 and DHG2, but with extended controls, including those previously found only on the back panel, such as pitch bend ranges, plus the additional LFOs. This Extended Control view also allows controls formerly on the back panel to be automated and Remote™ controlled
  • +Acidman FX: single DHG edit, switch-able between DHG1 and DHG2, with the Acidman FX array, the classic Harmonic Synthesizer version 1 view
  • Two additional LFOs:
    • LFO 2 uses the Oscillator 2 Tremulant Shape, but has its own Rate control. It can be sent to up to three predefined internal targets or to CV outputs, and can also be used to override (“O-R”) the standard LFO 1 rate used by Oscillator 2 voices, where it can be also be sent in mono or polyphonic LFO modes. Non-voiced targets are only available as a monophonic LFO

    • LFO 3 has its own dedicated Rate, mono/poly voice Mode and Tremulant Shape, and when enabled (“O-R”) overrides both the standard LFO 1 Rate and fixed Sine waveform used by the Filter Tremulant


  • Acidman Reverb now has two additional parameters, Pre-Delay and Density.
  • The Reverb Mod amount has been tweaked and now has a far bigger range
  • New anti-aliasing engine with better rejection of aliasing frequencies and up to 25% improved DSP performance
  • 16x Oversampling option added to Oversample control. Please note this is extremely CPU intensive and will be for bouncing or final rendering only in most usage scenarios, although be aware increasing Oversample can change the timbre of the Noise Generator function. You may prefer to leave Oversampling off, at the default 2x, or increase slightly to 4x when making extensive use of the Noise Generator
  • Over 60 “2nd Edition New Sounds”. Also re-categorised the less static “Pads” into more appropriate “Textures”, or even “Poly Leads” sections
  • Bug fix: High Attack curves (extreme logarithmic) could prevent the decay and sustain stages of the amp envelope triggering
  • A copy of the long-thought-lost original spirit dupe of the Harmonic Synth v2 update feature set has been added to the user guides!


  • Pitch Bend Ranges can now be automated or controlled via Remote™. See updated User Guide Addendum sheet


  • Fixed an issue where the new velocity value of CV Gate inputs could result in incorrect note velocity


  • Added a velocity curve option: Low curve/Linear (original default)/High curve
  • The correct font is now used on the main control panel labels
  • 50 new repatches, including the new Textures folder, plus a Pulsar-based Combinator for each of these extra patches in the new Combinators/1.1 Patches/ sub-folder.
  • Bug fix: notes are now released correctly when using the “Dual Arp” Player in Reason 9+
  • Signature repatches have been duped into the appropriate type folders for easier “by type” browsing


  • Fixed smoothing rate of distortion gains


  • Osc 1 ring mod signal was incorrectly applied with the Osc 1 amp envelope; it now ignores the envelope
  • Fixed an issue with voice release handling in Poly mode





Gorgeous and Grandiose
Mats Karlof
Ex-Imperial Stormtrooper
A fine device, OF COURSE. 🙂
Jon Heal
I was looking for an RMI Harmonic Synthesizer plugin, and came upon your site. Back in the 70's I was an authorized RMI dealer. Nice work on the original songs on SoundCloud! Some really lush sounds there.
Vincent M
I really enjoy it.
That new JPS harmonic synth sounds super sweet in all its old school 5-bit glory 😉
Paul van der Heijden
I just love this synth! 😀
I'm a proud owner of this incredible synth, and I'm an admirer of Jean Michel Jarre. Never before with these unique racks in the world have I felt so close to my favorite international artist. Thanks!
[v2] Amazing update. A great synth just got much better.
I love this synth. Thanks for the FREE update!
Gorgeous, oldschool, full-featured, reasonized.
This sounds outstanding, I had goosebumps. Well done!
You guys did a fantastic job on this - WOW! Nice work!
A synth that looks like it's capable of dishing out a real electric shock to the unwary! Remind me not to poke about the back of it with a screwdriver. I can't wait to get my grubby paws on this to give it a thick coat of looking at.
This sounds and looks great!
Jeez, vibes all over the place! NICE! I love this non clean sound. Warm and funky. Superb interface too. Killer!
Marco Raaphorst
This synth is really special and not common like the most other 3rd party synths
Sizzle my sausage! - I just listened to the demos, this sounds amazing!
This is one of those instruments that sit very well in a mix. It adds a depth/dimension apart from most of the other instruments that I have heard and purchased.

Trial, Buy Now, or Rent-to-Own