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Future Audio Workshop Circle

Software Synth [Mac/PC]
Published July 2009
By Nick Magnus

Future Audio Workshop's debut soft synth offers versatile modulation possibilities, via an interface designed to be highly intuitive.

Future Audio Workshop Circle

With so many software synths out there, it must be a challenge for manufacturers to come up with fresh ideas that will tempt musicians to part with their hard‑earned cash. Most self‑respecting DAWs already include some sort of proprietary virtual analogue synth amongst their plug‑ins, and these are often very capable and well specified, like the Z3ta+ synth that comes bundled with Sonar.

We are, it seems, positively spoilt for choice — so what sort of features might tempt musicians to spend money on yet another virtual analogue plug‑in synth? How about ease of use, flexibility, a highly visual approach to creating sounds and educational value for starters? Irish company Future Audio Workshop address all these points with their first software synth offering, Circle.

First Circle

The Sounds tab displays a preset list based on sounds' class, type and style.The Sounds tab displays a preset list based on sounds' class, type and style.

FAW seek to impress from the outset with Circle's opulent packaging — I was almost expecting the box to contain some deliciously evil Belgian chocolates! Even the owner's manual is printed on high‑quality, semi‑glossy paper. Once installed, Circle initially runs in demo mode for 20 minutes, after which time it goes out of tune. Saving is also disabled. Activation for permanent use is by the familiar on‑line challenge/response method; an activation file to unlock the program is returned by email. Circle runs on Windows XP and Vista (32‑bit) and Mac OS 10.3 or higher, in stand‑alone, Audio Units, VST and RTAS versions.

Graphically, Circle is rather striking. The overall mood is black, punctuated with bright colours that leap out of the user interface. The main screen contains the various synthesis modules, laid out in three vertical columns. Each column deals with the fundamental components of analogue synthesis. The left-hand column contains six sound sources: four waveform oscillators, a noise source and feedback. The central column comprises five modifier modules. The first and last of these are fixed as source mixer and VCA level but the middle three modules offer interchangeable options, of which more later. The right‑hand column hosts five modulator modules, all of which offer three interchangeable modulator types. Note that the first four oscillators and the noise module (but not feedback) can also be used as modulators in their own right, in addition to those in the modulator column.

Like A Circle In A Circle

The Keyboard tab shows controls for the arpeggiator, key follow and glide times.The Keyboard tab shows controls for the arpeggiator, key follow and glide times.

The key to Circle's ease of use is the way in which modules are patched together — and this is also the inspiration behind the Circle name. Inside each of the 10 possible modulation source boxes is a uniquely coloured circle and every possible modulation destination has one or more grey 'receptor' circles beneath it. To patch a modulator to a destination, simply drag a modulator's coloured circle with the mouse, and position it over the desired receptor circle. The receptor circle lights up with the modulator's colour, and the effect of your patching is heard straight away. It's analogous to plugging in patch leads on a modular synth, because you can see at a glance what is patched to what, but without the tangle of physical cables getting in the way. Any single modulator can be patched to an unlimited number of destinations, which would be impossible using physical patch cables on a hardware synth without a copious supply of voltage‑control splitter modules!

To adjust the depth of modulation applied to any destination, click on its receptor circle and a vertical fader appears. This can be dragged up and down to apply varying amounts of positive or negative modulation. An outline around the receptor circle gives a visual indication of how much modulation is being applied. To 'unplug' a modulation routing, you simply drag the coloured dot away from a receptor circle, and the connection will be broken.

Modulators can also modulate certain aspects of other modulators, too; for example, an envelope can modulate the speed or depth of an LFO. Surprisingly, you cannot modulate envelope modules, except via MIDI control messages.

Source Modules

Settings for polyphony, master tempo sync and patch randomisation.Settings for polyphony, master tempo sync and patch randomisation.

The first four oscillator modules each provide a large selection of waveforms, in a choice of 'analogue' or 'wavetable' flavours. Analogue‑style waves are available in four shapes: sine, saw, square and triangle, the latter two shapes having variable pulse width. The choice of wavetable waveforms is somewhat larger: 110 waves, ranging from classic analogue shapes to bright, aggressive and enharmonic types and beyond. Circle's wavetables are single-cycle waveforms, very much like those of Korg's DW8000 'digilogue' synth from the early '80s, as opposed to the sequenced wavetables found in Korg's Wavestation or PPG's famous Wave wavetable synth. However, Circle has various waveform‑morphing tricks up its sleeve. Two different wavetables can be selected for each oscillator, an upper wave and a lower wave. A corresponding crossfade slider morphs between the two, allowing for a wide variety of intermediate shapes. The crossfade slider can be modulated, enabling automatic morphing between the upper and lower waves using an LFO, envelope, sequencer, key position, velocity, or even another oscillator. Given that the waveform mixer has three modulation receptors, some fairly extreme timbral gymnastics are possible, just from a single oscillator.

Oscillators can also be hard‑sync'ed together in pairs, and any of the four oscillators can be switched to 'sub' mode, turning it into an LFO with an almost limitless variety of morphable shapes available from the wavetable waves.

The fifth oscillator is a noise generator with low or high Range option and tunable frequency. Source six (Feedback) is not actually an oscillator, but takes a feed from after the VCA and pops it back into the beginning of the signal flow at a variable level. Feedback's tuning can be adjusted over a four‑octave range, and modulating this tuning produces some really outrageous and aggressive flanger‑like timbres that make sync'ed oscillators seem rather tame by comparison.

Modifier Modules

The three series‑linked effect slots are freely configurable from a choice of seven effects.The three series‑linked effect slots are freely configurable from a choice of seven effects.

Although modifier modules one and five have fixed duties (as explained earlier), modules two, three and four have various options available. Module two (the pre‑filter modifier) and module four (the post‑filter modifier) each have the same choice of eight different effects — not to be confused with Circle's separate Master Effects. Options available are mouth filter, fuzz distortion, overdrive, parametric EQ, shelving EQ, phaser filter, crusher and ring modulator.

The mouth filter is particularly interesting, adding formant qualities to the waveforms. A fader transitions between three vowel 'slots' into which different vowels (AH, EE, OH, UH or EU) are placed. When the fader is modulated, moving vowel sounds are produced, either in free-time or in sync with your song if the modulator is sync'ed to the host DAW's tempo. Fuzz distortion and overdrive are unusual in that the effect appears to be applied separately to each synth voice. They both serve to 'roughen up' the waveform, yet you can still play intelligible chords. The result is interesting, but not quite what you might expect. The difference between fuzz and overdrive effects is maybe a bit too subtle, because they sound absolutely identical to me!

The Parametric EQ has two bands with variable gain, frequency and Q, while the shelving EQ provides gain control over the low and high frequencies. The phaser filter is a comb filter with adjustable frequency and resonance. The crusher bit‑crushes the waveform to destruction if that's what you want, and the ring modulator does exactly what it promises, producing everything from shimmering tonal vibratos to sharp, metallic and enharmonic timbres.

All of these effects have a mix control, to balance between the untreated and treated waveform, and an output level control. Usefully, effects settings can be saved as snapshots, and reloaded whenever required.

Module number three is the all‑important filter, selectable as either a single or a dual filter. The single filter has a choice of low‑, band‑ and high‑pass types, in two‑pole and four‑pole flavours, with cutoff frequency and resonance. The dual filter doubles up on this, with the option to arrange the two in series or in parallel, each filter having its own modulation receptors.

Modulator Modules

Each of the five modulators can be one of three types: either an envelope, an LFO or a step sequencer. This flexible arrangement means that if you want all five to be envelopes, then go ahead — you can have them. Any combination of types across the five modules is possible.

The envelopes are of the standard ADSR type, with an additional parameter called 'snap'. Snap adjusts the slope of the attack, decay and release stages from linear to exponential, making it possible to fine‑tune the envelope response.

LFOs have 16 basic waveforms to choose from; like the oscillators, LFOs have independently selectable upper and lower waveforms, together with a crossfade slider to morph between the wave shapes. An animated graphical display shows the resulting waveshape, as well as indicating the LFO speed. LFOs can be sync'ed to host tempo and include adjustable delay time and fade‑in time.

The step sequencers, although simple in essence, offer numerous ways of injecting movement and interest, even to a basic single‑oscillator sound. A sequence comprises up to 16 steps, whose values can be displayed either as arbitrary positive or negative values, or as semitones. The sequence can sync to host tempo and a smoothing control softens the transition between steps, 'gliding' between step values. Obvious applications are to have oscillators play a musical phrase, or to modulate the filter cutoff frequency. The fun really starts when using the sequencer to modulate the mouth filter to create rhythmical 'talking' effects. And when applied to other parameters such as the oscillator's wavetable mixer, oscillator sync or the ring modulator's frequency parameter, effects not unlike the PPG's animated wavetables can be obtained.

Wait, There's More...

Along the bottom of the main screen are five tabs which expand when clicked on. First up is 'Sounds' which provides the means to search your preset collection via a list of predetermined sound characteristics. Highlighting one or more characteristics provides a list of qualifying presets that share those criteria in the results pane. Presets can be organised into banks and you can create your own banks, delete them and assign character 'tags' to your own presets.

The Keyboard tab provides control over key follow, offering two independent key follow slopes. The grey slope defaults to a linear shape, which would typically be used to govern how an oscillator's pitch follows the keyboard. The blue slope could, for example, control the filter's cutoff frequency relative to key position. Either slope can, of course, be used to modulate any parameter that can be modulated, and each slope provides three breakpoints that can be moved to reshape the slopes as you see fit. Circle generously provides a glide (portamento) control for each key-follow slope — a very useful bonus.

Circle's arpeggiator is also found in the Keyboard tab, and is a fairly basic example of its type, offering up, down, up/down and 'as played' varieties. There is also control over note length, swing and shift (octave range). Arpeggios can also be sync'ed to host tempo, but certain problems arise here. With sync switched on, the arpeggiator drifts out of time after only a few bars, and applying any amount of swing throws it completely out from the word 'go'. A little additional work is need here, perhaps.

In the Settings tab, Circle's Randomise feature is a handy means of creating off‑the‑wall sounds when inspiration is at a low ebb. The degree of randomisation can be separately specified for sources, modifiers, modulators and master effects, and any of these can be excluded from the randomisation process.

The Voicing pane determines a preset's polyphony up to a maximum of 32 voices, with the facility to specify the number of Unison voices, also up to a maximum of 32. With Unison set to 1, so that each note uses one voice, Global Detune runs the gamut from subtle detune between voices to 'totally trashed'. When Unison is set to two or more voices, Global Detune can subtly or dramatically thicken the sound — perfect for those trance-anthem lead sounds. The drawback to this, in contrast to other synths that have a detunable 'super‑saw' waveform, is that Circle uses many more voices to achieve this effect, resulting in a considerable CPU jump.

Extra Effects

The Effects tab contains the Master Effects, up to three of which can be applied to a patch. Each effect slot has a choice of phaser, reverb, echo, double echo, ping‑pong echo, chorus or panner. The effect slots are connected in series, so the order in which the effects feed each other should be taken into consideration. Space does not permit a full description of every effect, but with certain exceptions these perform much as you would expect.

The three echo effects vary in the following ways. Echo has a single, variable delay time, and the delayed signal has a subtle stereo width applied. Double echo is a stereo delay with separate left and right delay times, while ping-pong echo has a variable initial delay time (the ping) followed by a second variable delay that bounces back and forth in stereo (the pong).

Panner is a simple pan module that can be modulated for those Rhodes‑like stereo tremolo effects. Phaser is similar to the modifiers' comb filter effect, with up to six stages, resonance, and its own in-built modulation. The chorus is mildly disappointing, sounding curiously bland. This may be due to an apparent bug in its modulator waveforms: the sine-wave modulation behaves correctly, but the 'square' wave actually performs a sawtooth in the right channel with barely any movement in the left, whilst the sawtooth wave fails to modulate at all.

Lastly, the reverb is a rather strange beast, and quite unlike the smooth digital reverbs we've come to expect. There is a significant amount of chorus‑like modulation inherent in the reverb signal, and while short reverb times produce passable room‑like ambiences, longer reverb times have an unpleasant out‑of‑tune character, reminding me somewhat of early guitar stomp‑box reverbs.


Circle has much to offer the inquisitive synthesist, and is equally at home producing both 'traditional' big, fat analogue synth sounds and those of an experimental nature. However, the factory presets arguably tend to lean too much towards the quirky and experimental, giving the impression that Circle sounds rather cold and clinical. This is not the case, and it would be good to see some more 'bread‑and‑butter' analogue sounds amongst the presets to prove the point.

Circle's approach to connecting modules is highly intuitive, and is sure to provide both novice and experienced synthesists with much inspiration, not to mention moments of enlightenment and a sprinkling of happy accidents. During the course of programming, additional modulation possibilities and other features occur to you that don't exist in Circle's current form, and as such, it could be seen as a work in progress, with potential to grow.

Despite a number of bugs and the occasional oversight, Circle is immensely absorbing and enjoyable to use, so what better reason could you need to download the demo version and give it a spin?  


The number of modular and semi‑modular soft synths is growing constantly, all offering their own particular set of bells and whistles, and with varying degrees of depth and complexity. What Circle has to offer is a modus operandi that makes it very easy to program, and as such it's not easy to point to any other exact equivalent. Personally, I feel that Rob Papen's Blue is fairly close in sound and comparable features, including wave‑morphing and step sequencer modulation. However, it is not truly modular, in the sense that the number of modulator types is fixed, with none being interchangeable; and with operations being spread out over several pages, the structure of sounds is not immediately visible from a single screen.

Endless Waves

Want more wavetables? No problem. A separate applet called the Circle Wavetable Generator can be downloaded from FAW's web site, and allows you to create your own wavetable waveforms from any WAV file. Of course, only single‑cycle wavetables are generated, so forget the idea of transforming that magnificent Steinway sample into an authentic‑sounding piano waveform. Nevertheless, some interesting and serendipitous waves can be generated from practically any WAV file, and these can be automatically added to Circle's wavetable list with a single mouse click. The scope for creating your own wavetables is therefore virtually infinite.

FAW worked closely with artist and sound designer Andrew Souter, of Galbanum, to create Circle's wavetables, and a suite of over 1800 of them can be purchased from A demo bundle of these can be freely downloaded from FAW's web site, giving some idea of what's on offer.

MIDI Control

MIDI control of Circle is nothing if not comprehensive: pretty much every parameter can be assigned a MIDI controller, with multiple assignments from a single controller being possible. Assignments are made using the familiar MIDI learn method, and all assignments are displayed by name in the list in the Control tab. Minimum and maximum ranges can be set for each assignment, with the option of making them specific to the current preset or global to all presets. There is, however, one standard control function inexplicably missing from Circle: the MIDI sustain pedal. Hopefully this basic but essential keyboard control will be implemented in future updates.

Mac users also have the ability to control Circle using the OSC (Open Sound Control) protocol, allowing control surfaces such as the Jazz Mutant Lemur to be integrated. A Circle control template for the Lemur can be downloaded from the FAW web site.

Published July 2009