VST Review: Circle² Software Synth by Future Audio Workshop w/ Rory PQ

In this VST plugin review, Dubspot’s Rory PQ takes us through the new Circle² semi-modular software synthesizer by Future Audio Workshop. Get an in-depth look at the new features that make this powerful, modern software synthesizer a tool worth adding to your arsenal.


“Circle² the powerful easy to use software synthesizer.” ~ FAW

In 2007, the Ireland-based audio software company Future Audio Workshop (FAW) set out with a mission to help spread the playing, producing, and listening to music through the medium of computer technology. In 2009, their hard work and dedication conceived Circle, an innovative software synth that combines powerful digital oscillators and wavetables with an analogue-style semi-modular architecture. Since its release, Circle has garnered the attention of renowned artists such as Deadmau5, Jimmy Edger, Richard Devine, Mike Huckaby, and many others.

2015 marks the launch of Circle², the latest major update to Future Audio Workshop’s flagship software synthesizer. The new update is extensive delivering a fully re-written audio engine, redesigned interface, several new features, impressive new modules, effects enhancements, as well as an extended sonic palette of sounds.

Circle²’s esteemed user-centred design approach is forward-thinking and highly intuitive providing an improved workflow and user experience for both novice and experienced users. The unique interface reveals every parameter in a single window that is very accessible and easy to operate without having to click around to find hidden controls and submenus. The complex sounds crafted from the simplistic operations of this modern looking synth allows the user to focus on creativity rather than technicalities, which makes it a must have tool for your arsenal.

Circle²’s Main Interface


Circle²’s improved interface is fully Retina display ready, bringing a vibrancy and clarity that is not available in other software instruments. The functionality of the interface is grouped into three different sections on the main interface, the Top Panel, the Main Panel, and the Bottom Panel. Let’s take a brief look at some of the controls and features of these three sections.

Top Panel – This section provides a lot of the operations that are regularly needed, such as master volume, saving, details about the currently loaded sounds, and various MIDI options.

Main Panel – This section is the heart of Circle²’s interface and is where you design your sounds. This panel is where all the modules and their related controls and settings are located.

Bottom Panel - This section displays the keyboard modulation outputs along with buttons to access more advanced settings. The additional features include the Preset Browser, Preset Manager, The Arpeggiator, Keyboard settings, Master Effects, and various other sound engine controls and OSC settings.

Circle²’s Main Modules

Circle² is capable of producing an incredible amount of changing sounds. To produce these sounds, Circle² has different modules that are combined and modified in different ways to produce and effect unique tones. In total, Circle² has the possibility to have 32 single notes or voices playing at the same time and comes with over 200 pre-made sounds easily found in a clever sound Preset Browser. The three module sections located on the Main Panel include the following:

Source Modules – The section located on the left is where all the modules used to produce and create sound are grouped. The sound sources include an Analog Oscillator, Wavetable Oscillator, VPS Oscillator, Noise, and Feedback modules.


Modifier Modules – The center section of Circle²’s main interface is where all the modules that affect or change the sound produced by the Source Modules are grouped together. The Source Modules are used to apply various effects and other types of processes to shape your sounds. The updated sound modifiers include a Mixer, Mouth Filter, Fuzz Distortion, Overdrive, Parametric EQ, Shelving EQ, Phaser Filter, Crusher, Ring Modulator, Analog Filter, Dual Filter, and VCA control.


Modulation Modules – The section located on the right is used to control Modulations for various parameters. The Modulation Modules have parameters to modulate sounds with an ADSR Envelope, LFO, Sequencer for step modulation, and Keyboard Follow for note tracking.


In addition, Circle² ‘s modules have a unique ability to show visual feedback for current settings in real-time. For example, you can visually see Circle²’s LFO rate change when you turn the Rate knob. You will see the waveform speed up or slow down depending on which way you turn the knob. Personally, I like watching the circle follow the ADSR Envelope. You can visually see how long or short the attack, decay, and sustain are set, as well as see how the release reacts once you let up on a note. This feature is great for novice sound designers learning how ADSR Envelopes work!

Modulation with Circles


Modulation is one of the key elements of creating sounds with Circle². Each module in Circle² that produces modulation all have large color- coded circles, which represents the output of the modulation. What makes modulation so fun in Circle² is you can simply drag the output circle of a Modulation Module and place it in any empty modulation input slot underneath the desired knob or control you wish to modulate. For example, you can modulate the filter frequency with an LFO by clicking and dragging the circle located in the upper left area of the module and placing it underneath the control you want to modulate. It’s that easy! Also, you can even preview how the modulation will affect a sound by hovering a circle beneath a knob. No other synth I know of has this brilliant feature. It allows you to explore sounds in a truly intuitive way.

Managing Sounds


The Preset Manager can be accessed by clicking the “Sounds” button on the Bottom Panel. Revealing this pane will give you options to manage, group, and search for your desired sounds. The browser filter is an easy way to find sounds fast based on sound characteristics criteria. For example, you can filter results for a piano sound that is soft and from the 1970s by clicking the relevant buttons in the filter selection window. All sounds that match these criteria will display in the search results panel. You can even create personalized criteria by simply pressing the “Characteristics” button and highlighting the criteria you want to add to the sound. Another way of opening sounds in Circle² is to use the Preset Browser drop menu in the Top Panel. This drop menu contains a tag cloud and search text box so you can easily locate the sounds you require. Although sounds are accessible here, all editing of characteristics and tags are carried out in the Bottom Panel through the Preset Manager.

Master Effects


After you design your sounds, you can add additional effects to the full mix of sounds with Master Effects. The Master Effects can be accessed by clicking the “Effects” button on the Bottom Panel. You can also attach modulation to many of the most important parameters for even more modulation possibilities. For example, you could attach an LFO to a master effect Pan knob. The Master Effects include Phaser, Reverb, Echo, Double Echo, Ping Pong Echo, Chorus, Panner, Bucket Delay, and Tube Distortion.

The Keyboard Tab


The Keyboard Tab is where everything related to notes and your keyboard are grouped. It can be accessed by clicking the “Keyboard” button on the Bottom Panel. Revealing this pane will allow you to access the Arpeggiator, Virtual Keyboard, Keyboard Follow Graph settings for keyboard follow modulations, and Keyboard Follow settings for more advanced keyboard follow parameters.

Settings and Control Tabs


The Setting Tab and the Control Tab are also located on the Bottom Panel can be accessed by clicking either the “Settings” or “Control” buttons. The Settings Tab has parameters to control the global voicing, tempo sync, and a randomize function for generating random sounds. The Control Tab has available settings related to controlling Circle² using hardware controllers, such as MIDI or OSC enabled touch screen controllers.

New Features in Circle²

  • VPS Oscillator (Vector Phase Shaping) – Unique to Circle², this new type of oscillator brings you a new type of synthesis designed by a partnership between FAW and the audio research group at Maynooth University.
  • Totally redesigned interface that is Retina ready and optimized for creative flow.
  • Performance enhancements and improved sound via a fully re-written audio engine that delivers better tone with improved low-end depth and increased high-frequency clarity.
  • Improved Preset Browser that utilizes tags and search options for quick and easy preset management.
  • New factory preset bank with over 200 presets complete with modern sounds ready for use in your music.
  • Visual Sound Design by moving the colour-coded circles around the interface to start creating unique sounds. Preview a connection by hovering a circle beneath any knob.
  • New Bucket Delay and Tube Distortion modules.
  • Utilizes the latest version of JUCE audio framework, resulting in a more stable and future proofed Circle².
  • Now official support for Reaper, Studio One, and Bitwig Studio.
  • Full 64bit and 32bit support, both on Windows and OSX.
  • Free upgrade for all existing Circle users.

Purchase Info

New License: €99.00/$129.00 | Free upgrade to existing Circle users

Demo Download Links



Additional information on Circle² is available at:


About Future Audio Workshop

Future Audio Workshop is a vehicle for realizing ideas and visions for innovative audio software and hardware. Since the company’s inception in June 2008, Future Audio Workshop has released a wide range of different products, including a music identification system for nightclubs, the first DJ application for iPhone and a synthesizer that has been used on hit records by many prominent artists. The team is agile and dynamic, with backgrounds that range from software engineering and hardware design to academia and the music industry. Our work has been featured in Resident Advisor, Vice Magazine, FACT Magazine, Wired Magazine, Music Radar, and Sound on Sound.

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