Circle is one of the most ambitious soft synth designs I’ve seen yet. Its core features read like a wish list for what a modern soft synth would do:

• On-screen routing designed for the computer screen, with color-coded circles, drag-and-drop, previews — and no silly virtual cables. (Sorry, Propellerhead.)
• OpenSoundControl support for the Monome, Lemur, Wacom tablets, whatever you’ve got — along wih easy MIDI learn.
• “Live performance”-optimized UI — actually very much a kindrid spirit with tools like Ableton Live or FL Studio in design aesthetic, workflow, and accessibility, but in a synth — just the thing if you’ve felt a gap between the sequencing workflow and the synth / sound design working method. And you can even swap presets with an Apple Remote if you’ve got one.
• Easy sound design (more on this soon)

The sound engine itself is a good survey of the kind of tools you might want, with a mix of analog- and digital-style waveforms and modulation, but plenty of oddball wave shapes and modulation and effects thrown in, too.

What I like best about developer Future Audio Workshop’s approach: rather than be the most powerful or the most sonically unusual or the most feature-laden instrument, they want you to achieve a sense of creative “flow.”

But I really can’t talk about the instrument very well as a result — have a look at the demo videos, and I think you’ll be as intrigued as I am. (I’ve been working a little bit with an early build, and really like it a lot.)

Future Audio Workshop (skip to the videos, really)

Mac / Windows (Intel, Vista, AU, VST, RTAS)

Pricing TBD (but expecting a fairly reasonable price point); available soon

Stay tuned, as I’ll be making some music with this software over the coming days and want to report back in more detail — particularly when it comes to evolving OSC connectivity for hardware like the Monome (and software connectivity, too, naturally — would be great to couple this with Reaktor, for instance).

If you’re at Musikmesse in Frankfurt, stop by and say hi to the developers. They’re also keeping a Flickr stream of the new goodies at the show — not just theirs. Hope they’re able to break away from the booth and look around.