Under the EXB-Radias' Hood

The EXB-Radias expansion was one of the things that attracted me to M3.  I figured it would enable it to be a good replacement for my SH-201 in my gigging rig with Full Moon Fever.  Now that I've familiarized myself with it, I've come to realize that its a lot more than just another virtual analog synth.  The "multiple" part of Multiple Modeling Technology is not just marketing bullshit.  The EXB-Radias also adds formant synthesis which synthesizes human voice sounds; vocoding; a simple version of FM synthesis; and single-cycle sample playback synthesis.

Every section of the Radias synth architecture has bells and whistles that do interesting and unusual things. 

One of the Radias' two oscillators (Oscillator 1) does a whole lot more than produce simple analog modeled waveforms.  It also provides:
  • DWGS - Yet another Korg acronym that stands for "Digital Waveform Generator System".  This technology has roots going all the way back to 1985 when Korg introduced the DW-8000.  Basically, it adds single-cycle digital waveforms as raw sonic material produced by Oscillator 1 in addition to the usual complement of analog modeled waveforms.  There are actually some very nice, useful waveforms available including organ, e-piano, guitar, bass, noise, and alternate analog-style waveforms.
  • Formant - As I said, this waveform simulates a human voice and includes parameters that control the vowel sound produced and the size of the mouth!  And without even opening up the built-in vocoder (which sounds fantastic BTW).
  • Audio In - Let's you route external sounds through the synth engine.
  • Oscillator Modulation - If you select an analog-style waveform for Oscillator 1, the Radias provides parameters to modulate the waveform itself, conceptually similar to what PWM does with pulse waves.  It also lets you cross-modulate Oscillator 1's frequency using Oscillator 2's output (essentially creating 2-operator FM synthesis).  It provides a Unison mode with detuning using a single oscillator (like Roland's SuperSaw waveform only it can be done with any analog modeled waveform, not just sawtooth waves).  Finally, its provides something called VPM (Variable Phase Modulation), which uses a sine wave at a harmonically-related multiple of Oscillator 1's frequency to modulate Oscillator 1's phase.  I haven't experimented with this yet, but it is supposed to produce metallic-sounding overtones.  All-in-all, Oscillator Modulation gives you the ability to mangle the heck out of a waveform before it even gets to the filters, amplifier, or effects.  And all this, is within a single oscillator!  There's still another oscillator (albeit a more normally-specified one) and a noise-generation source left.  And once you do add in the 2nd oscillator, you get oscillator sync (for that squelchy Cars lead synth sound) and ring-modulation.
One of the Radias' two filters also has a very neat trick.  In addition to the usual set of  low-pass, high-pass, and band-pass filter types, it lets you continuously vary the filter between these types, interpolating the filter output so that the transition is smooth and seamless.  And of course this is a modulation destination controllable by any supported modulation source.  Very cool.  The other filter doesn't support type modulation, but it does have a comb-filtering mode that produces cool flanging type effects when you modulate the frequency.

The Radias synth engine also supports waveshaping.  In the UI, its organized within the amp section of the synthesizer, but its really not part of the amplifier, since it can be placed between the oscillators and the filters (leaving the amp in the usual post-filter location).  Essentially waveshaping in the Radias allows you to change the shape of the waveform in various ways, including sub-oscillator generation, electric pick-up simulation, and a bit-crusher setting.  Placing the waveshapper before the filter can produce a radically different sound than after.

Finally, in addition to "built-in" modulation routings such as velocity to amp level and joystick to LFO1 to pitch for vibrato control, there's Korg's "virtual patch cord" system, which does exactly what you think it does.  It emulates the patch cords used in a modular synthesizer, providing a very easy way to configure modulation routings.  E-mu provided a very similar system in their Proteus 2000 and its many variants (including my beloved PX-7 Command Station).  The E-mu implementation was more robust with more sources, destinations, and "modulation processors" (similar to Korg's AMS Mixer concept).  But the EXB-Radias implementation of this system is fine on version 2 of the operating system, which augmented the system with additional modulation destinations including all oscillator control parameters, all filter settings, EG parameters, and patch cord intensities.  With the v2 update, virtual patch cords supports most every modulation routing I'm likely to use, and many that I'm not.

My impression is that modulation is the key to unlocking the Radias' charms.  Most every one of these capabilities are controlled by parameters that are valid modulation destinations.  Heck, even the modulations themselves are modulation destinations!  By modulating these and the usual synth parameters, the possibilities for motion within a single timbre are just enormous.  Post mortems on some of the more interesting sounding factory presets confirms it -- single timbre sounds with independent evolving textures that sound like multiple synth layers. Right now, I feel like I understand the architecture pretty well, but I'm nowhere near having any sort of mastery over it.