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FM4 Frequency Modulation Synthesizer

Four Operator FM Synth

Primal Audio I/S

  • • 3 sound engines modelled on 1980s hardware units
  • • 4 operators configurable in 16 different routings
  • • 8 waveforms from classic hardware FM synths

Video clips

New in version 2.0: Eight new routings / 40 new presets.

FM4 is a four operator FM synthesizer for the Reason rack. Modelled on the first commercially available FM synths from the 1980s FM4 recreates that dirty, lo-fi, cutting sound of the original units. Combined with a carefully thought-out, stripped-down, yet powerfull, user interface, FM4 makes it a breeze to create a multitude of sounds - from punchy basses, crystal-clear bells, and lush pads, to organic textures, striking drums, and piercing leads.

Product details

At the heart of FM4 is our digital FM modelling engine which has been carefully modelled on original hardware units from the popular DX series. Every aspect of the hardware — from envelope curves to sine-table sizes and quantisation errors to digital-to-analogue converters — has been meticulously analysed. Combined with complex math and countless hours of tweaking parameters, FM4 provides the same gritty sound as the hardware. Moreover we have given FM4 a carefully thought-out, stripped-down, yet powerful, user interface. With every parameter being available on a single page, alike traditional analogue synthesisers, FM4 facilitates a workflow with minimal overhead, encourages exploration, and allows for faster programming yielding instant sonic results.


  • Four operators configurable in 16 different routings
  • Three sound engines modelled on 1980s hardware units
  • Eight waveforms derived from classic FM synths
  • 2x, 3x, and 4x polyphonic unison
  • Numerous CV inputs/outputs for external control
  • Unique drift parameter for creating organic sounds
  • Operator wave phase modes: sync, free & random
  • LFO with 5 waveforms and tempo sync
  • Pitch decay envelope with varying curves
  • 100% free of farty brass-sounds
  • 200 patches

Update v. 1.1.0:

  • Fixed CPU-issue on Reason 7.1.
  • Added a new clean-model.
  • Added 40 new combinator patches.

Update v. 2.0.0:

  • Added 8 new routings.
  • Added 40 new factory presets.
  • Bug-fixes.

All product names used are trademarks of their respective owners, and reference to these here in no way constitutes an association or affiliation with Primal Audio. All trademarks are solely used to identify the products whose sound was studied during the development of FM4.



Released: 2016-12-08
Version: 2.0.0