Sound sources along the left are mixed (top center) and sent through three multi--effects for filtering and -distortion. -Modulators on the right are assigned by dragging color coded dots to inputs near the affected controls.
Circle ($199) is the first product from the Irish collective of developers Future Audio Workshop (FAW). It is an analog-modeled synth that comes in standalone and plug-in formats (VST, AU, and RTAS) and boasts a variety of unusual features. Two things make this synth special: it sounds great, and it's easy to program. Audition it by listening to the Web clips on the FAW Web site or downloading the full-featured demo.
Circle ships with more than 500 factory presets and a detailed PDF manual. It's easy to figure out what's going on by examining a few presets and playing around, using the manual as backup for the more enigmatic settings. The preset browser and various ancillary panels are accessed with tabs along the bottom of the user interface. Presets are categorized in the browser by 21 characteristics (Bass, Pad, Moving, Static, 1970, FX Sounds, and so on), and you can characterize your own presets as you create them.
The left side of Circle's control panel is devoted to sound sources: four oscillators, a noise generator, and a feedback circuit. The feedback is taken from the end of the signal path and passed through a short delay line that you tune in semitones. It produces resonator-style effects when applied to simple waveforms and gravitates toward distortion when applied to more-complex sounds.
The oscillators toggle between analog and wavetable modes. In analog mode, you get sine, sawtooth, and variable-width pulse and triangle waveforms. In wavetable mode, you choose two single-cycle waveforms from a selection of 110 shapes, and then use a slider to morph between the two chosen shapes. All of Circle's modulation options can apply to that slider, giving you a lot of sonic flexibility and motion.
A mixer at the top of the center column of modules mixes the active sources (you can turn any Circle module off to save CPU) and feeds the mix to three sound modifiers in series. The top and bottom modifiers are multi-effects emphasizing filtering and distortion. The Mouth Filter is an interesting example; an automatable slider morphs through three vowel formants. Those modifiers surround a resonant multimode filter module that you configure as one filter or as two filters in series or parallel.
The signal path ends in a series of three global multi-effects that can host the usual suspects: phaser, reverb, echo (single, double, ping-pong), chorus, and panner. They're nothing special, but they get the job done.
MOVING RIGHT ALONG
Circle's modulation scheme is another standout feature. Five control-rate modulators line the right side of the interface. You can configure each modulator as an ADSR envelope generator, an LFO, or a step sequencer. The modulators are color coded, and you apply them by dragging a colored ball to an input circle located below or next to the knob or slider you want to modulate. Once modulation is applied, clicking on the input circle reveals a bipolar slider for setting the modulation amount.
The sound source modules also have modulation outputs that you can use for audio-rate modulation (think FM). The oscillators have a subaudio mode, and that lets you use the unusual wavetable waveforms as LFO shapes. User-configurable curves tracking the MIDI keyboard (2) and MIDI Velocity (1) round out the modulation scheme.
You get a simple but robust MIDI controller setup. Clicking on the MIDI Learn button outlines each target. Click on a target, and then tweak a control on your MIDI control surface to assign it to the target. The subpanel revealed by the Control tab lets you set a range for each assignment. You can assign the same MIDI controller to multiple targets with different ranges. In a nice touch, even the individual steps of the step sequencers are available as targets, letting you automate step sequencing in real time. In addition to MIDI modulation, Mac versions of Circle support Open Sound Control (OSC).
Like most virtual instruments, Circle lets you randomize its settings and tame the results with separate amount settings for sources, modifiers, modulators, and master effects. You can also specify that tuning (sources) and levels (others) not be randomized.
Circle's clearly designed user interface, easy-to-use modulation scheme, and full-featured MIDI implementation make it a pleasure to work with. This is one synth that begs to be tweaked, and there's not much head-scratching involved. You're bound to find useful sounds among the many presets for your synth leads, basses, pads, and ambient effects, but you won't feel limited to the presets (see Web Clip 1).
Value (1 through 5): 4
Future Audio Workshop