FabFilter One Soft Synth

FabFilter One is a new virtual synth for the PC that offers basic monosynth functionality, but does it exceptionally well.

FabFilter One is the first release from FabFilter Software Instruments. FSI is a Dutch software developer, founded in 2002 by Frederik Slijkerman and Floris Klinkert. They felt that most software instrument companies had rushed into designing complex virtual synths, without putting enough emphasis on sound quality. FSI has taken the opposite approach, focusing on sound, and putting their effort into developing advanced filter techniques, smart parameter interpolation methods and a great oscillator.

FabFilter One is the first result of their approach. One strips virtual synthesis down to its basics. It is a monosynth with one oscillator, a LFO, one envelope generator and a filter. This approach makes One very easy to understand and put to use, but also limits the range of sounds it can generate.

The software installs very easily. The installer will add a standalone version of the application, in addition to a VST version. We tested FabFilter with Sonar, and had no problems with it.


Fabfilter is very easy to use. The interface is attractive and simple. Most options are available on screen at all times, eliminating the need to drill through menus. To get you started, FSI has provided a range of presets, ranging from basses to leads to techno sounds. While the presets are all good, it would have been nice for FSI to provide a larger number. This is not a significant limitation, though, since the synth is so simple to use.

fabfilter one

The synth has six main control sections: Oscillator; Portamento and Noise; Frequency Modulation; Filter; Envelope Generator; and Patching Features.

While FabFilter One’s user interface is very attractive, the arrangement of controls is a little counter-intuitive. Most synths group controls that affect one aspect of the sound together in sections, and have these sections follow the sound generation path from left to right. With FabFilter One, the modulation controls are on the right side, and some of the controls seem arbitrarily scattered around the interface. For example, pulse width modulation is in the same section as the oscillator, but frequency modulation is in a different section. Noise controls are spread among the Portament & Noise, Oscillator, and Patching Features sections. It also seems strange that the MG and EG modulation controls for the filter are in the Filter section, but the same controls for the Oscillator are in the Frequency Modulation section. A little more attention to consistency and historic precedents would help the interface.

While the interface layout is a little strange, it is easy to get used to, and users will quickly understand where to look for various controls.

FabFilter One offers flexible modulation of the oscillator and filter. The oscillator has several basic waveshape options, plus you can control the width of the pulse option. The basic pitch can be switched to one of four octave selections, and tweaked up or down 5 semitones. The oscillator’s pitch can be modified by the Modulation Generator (LFO) and the Envelope Generator, which can be used normally or inverted.

The filter controls are straightforward. The frequency control adjusts the filter cutoff, and the peak modifies the filter’s resonance. Controls are also provided for the level of the Modulation Generator (LFO) and the Envelope Generator.

The Patching Features section adds interesting flexibility to the patches that are possible with FabFilter One. This section lets you adjust the noise type, the source of the Pulse Width Modulation, invert the Modulation Generator, and change its shape and frequency.

Presets are available from a pop-up menu within the interface, which allows fast access, and Help is provided through a prominent button. The Help system is thorough, and implemented well.

The Sound

The bottom line for FSI is sound quality, and their focus pays off. FabFilter One has great sound quality. The filter is flexible and can create both smooth and aggressive sounds. The filter is a 12db/octave design, which gives it a relatively smooth and warm sound, with more subtlety than classic Moog or 303 designs. The highlight of the FabFilter One is the subtle gradations in the sounds it creates. As you open or close the filter, modify the portamento, or tweak the resonance “Peak”, there seem to be an infinite number of variations. One flows from one sound to the next fluidly, like classic analog equipment.

While the specs of the FabFilter are basic, it can create a large variety of sound, and do it very well. We put together a brief demo, below, that highlights some of the sounds it is capable of. The demo was created using five instances of FabFilter, including three for percussive sounds, and two for bass sounds.

Compatibility & Stability

We tested the standalone version, and the VST version within Sonar. Both versions were very stable, and were not overly demanding of the PC’s CPU. Within Sonar, we were able to easily use control envelopes to create parameter automation of various FabFilter one controls.

In our testing, we did not experience any crashes or glitches with FabFilter One.

FabFilter is also working on an Audio Units version of FabFilter One for Mac OS X, which they say will be released later this year.


FabFilter One offers very flexible modulation options for a basic single-oscillator monosynth, but only offers a single Envelope Generator. This was not uncommon in older monosynths, including some classics. However, it does limit significantly the range of sounds that can be generated. It would be nice to see future versions of the One include a dedicated Envelope Generator for amplitude (volume) modulation.


FSI is taking a step back from the rush to add ever more features to virtual synths, and is instead focusing on getting the basics right. With the FabFilter One, they have created a basic monosynth, but done it very well. A demo version of One is available at the FabFilter site.

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