The Korg Radias synthesizer was released in 2006, discontinued after a 4-year run, and seems to have polarized all its users. Some dismiss it as "digital crap", others hail it as a "future classic". Who is right? Are these people snobby analog purists? Is the other group Korg's minions, paid to drum up favor for this little silver beast?

I purchased the rack-mount model, the Radias-R, in 2006. I was relatively new to the world of "virtual analog" synthesis, and the sound of the Radias seduced me because it was so different. Think: bright, smooth, icy, crystalline, electrical.

There are many reasons to appreciate this synth. I'll summarize a few, because I want to skip to the heart of this post: The Radias contains 64 sampled waveforms ("SynthPCM"), and they're are a lovely, creative bunch, with lots of rich, cybernetic character. (Someone enjoyed designing these, I bet.) The comb filter is surprisingly useful and rich. Korg's free editing software is a joy to use.

Other features are likable, despite a few flaws: The 39 (!) knobs on the front panel don't rotate endlessly. The insert effects are impressive, but some of the best effects (the amp simulators) are restricted to monoaural output. The unison & stereo spread features are great, but you can't target them via the modulation matrix (yet you can twist those knobs in realtime).

There's also a snappy vocoder, which can vocode live input, or record input as "formant motion" and play it back. Unfortunately, recording is difficult, and must be triggered on the hardware. You can't scrub, or change the formant motion speed. The Radias can store 16 formant motions, but only 8 presets are provided. I hate to admit this, but most of them are tacky... (One of the presets speaks, "Yo! Everybody in the house, say 'Raaaaadias!'")

How Does It Sound?

The most important feature of the Radias -- which you will either love or hate -- is the character of its sound. My opinion is that anyone who describes the Radias as "deep" or "warm" is wrong, just plain wrong. The Radias is the opposite of warm, fuzzy analog. It is deeply cold, in an air-sanitizing sort of way. If iciness can be sexy, this is it.

The sound has a certain sonic distance, as if the phase of one speaker is inverted (but of course, it's not). The basic waveforms seem a bit sterile, even after summoning some analog trickery (detuning the oscillators, etc.) The sound is so smooth that it's practically transparent. This synth sits well in the background. With its bright character, I've been able to drop it into many mixes, and it magically sits well with minimal equalization. But my attempts to feature the Radias as the frontman have never felt satisfactory.

How did Korg craft this particular sound? I ran some experiments to figure this out. Here is my conclusion:

In most cases, the waveforms are not synthesized in realtime. They're pre-sampled.

The Formant provides a clue

The Radias has 9 oscillator types, including a Formant oscillator. (A formant is similar to a bandpassed sawtooth wave.) Here's the spectrum of a formant produced by the Radias, with the narrowest formant width available. (This spectrum was analyzed in Ableton Live.) This looks acceptable, you can see the prominent peak around 800hz:

However, when we increase the formant width, instead of producing a wider hump ... The peak splits into two peaks, with the same narrow widths as before:

By increasing the formant width further, the peaks move even farther apart:

Although the sound is pleasant, this is not a true formant. This behavior indicates that the Radias' "formant" is actually composed of two waveforms. These waveforms have been pre-sampled at various resonant peaks. The Radias produces its "formant" by playing two of these samples simultaneously.

The Sawtooth misbehaves

Another Radias oscillator type is the Sawtooth wave. When played at mid-range and high frequencies, the Radias delivers the expected sound -- a series of overtones marching up to infinity:

But something undesirable happens when we move down the keyboard. When playing lower notes, the high-end treble frequencies roll off:

Further down, it sounds even more muffled:

The Sawtooth waves are not being generated in realtime. They, too, are sampled. This sort of frequency roll-off implies that a sample is being played at a low frequency, and interpolated (a.k.a. "anti-aliased") to smooth the output. I'm not sure which window function Korg chose for the interpolation, but it is the driving force behind the Radias' character, as it filters every sound. Also note that the other fundamental waveforms (Square, Triangle and Sine) are sampled as well.

I suspect that waveform modulations (such as square wave's pulse width modulation) may be pre-sampled as well, since they exhibit the same roll-off. By sweeping the pulse width, the Radias may be interpolating between waveforms (like using wavetables). I can't seem to produce an audio demo to support this claim, so the wavetables may have hundreds of samples in them, too many for the human ear to discern.

However, the two effects based on frequency modulation ("Cross" and "VPM") do modulate in realtime. They produce appropriate spectrums, even when the oscillators run at low frequencies.

The Radias features a "morphing" filter, which can move between two filter shapes (for example, a lowpass and a highpass). This is probably achieved by processing the incoming signal with two "cardinal" filters (LPF24, LPF12, HPF, or BPF), and mixing their results together. I can't prove this, but the spaces between the cardinal points seem a little dull, as if phase artifacts are creeping into the treble, or the anti-aliasing artifacts are doubled.

These experiments helped me understand how the Radias acquired its sound. Short, single-cycle waveforms are looped and anti-aliased, resulting in smooth, hygenic timbres. Some of the longer samples (in the "SynthPCM" group) have more density, but they're still filtered by the anti-aliasing algorithm, which makes them sound airy and hollow. The Unison and Analog Detune features can add density, but in my experience, they don't add much thickness or richness, as it's merely playing multiple copies of the same smoothed waveform.

Hopefully this post doesn't read like Radias-bashing. I was more interested to discover Korg's tricks than anything else. The Radias is suited to some very specific genres and roles, and I wouldn't recommend it to everyone. Still, the sweet GUI editor makes this the most "fun", accessible synth in my collection, and I keep returning to the Radias for this reason alone.

To hear some creative Radias patches, check out Jexus' great YouTube demos: part 1, part 2.

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Like the era-defining DX7, the FS1R is an FM Synthesizer, but it boasts a massive 8 operators per voice, compared to 6 in the DX. And the FS1R sports a new toy, Formant Synthesis, capable of mimicking voices, human and otherwise! Waves and formants can modulate each other in 88 different configurations. Top that off with LFOs, filters, on-board effects... It's so flexible, and so complicated. So much power.

The FS1R was the last of Yamaha's FM synthesizers, and that's no accident. Even by 1998 standards, this thing dwells in a deep abyss of user-unfriendliness. Without a GUI, you must program 1,000+ parameters using 15 tiny buttons on the front panel. Fortunately, K_Take has developed FS1R Editor Software which lets you load/save patches, and twiddle the internals in real time (thanks K_Take!)

The unit sold poorly and was discontinued after 2 short years (long before a proper GUI emerged). I didn't know the FS1R existed, until Tavvv of the Braindead Monkeys mentioned it might be something my brain would enjoy -- Weird vocal effects! Technical crazy-sauce! Aural blasphemy!

Thus, the hunt was on. After two months, I had a single nibble -- a unit appeared on eBay, and I became its adoptive parent. (These units are scarce; only two units are listed on eBay at the time of this writing, and they're not getting any cheaper.) Was it worth it? Good question. If I had to describe this thing in one word, it would be: "Uhnnnhhhhh ... !!!"

After three months of use, I'm starting to comprehend this beast. With 8 operators (waves/formants) per voice, you must choose one of 88 algorithms. Here's a screenshot of a few (in K_Take's application):

Each operator has a zillion parameters: pitch and amplitude envelopes, a "skirt" (which makes the sound fuzzier), and wave shapes (sine, sawtooth-esque, square-ish, formants) which have another zillion parameters of their own. Also each voice has 8 "unvoiced" operators, which generate pitched noise. These imbue its "speech" with sibilance, and thus, consonants; A zillion more parameters.

Everything I just listed is actually quadrupled, as you control 4 voices per program. And you can use "formant sequences" to make the operators fly around and "talk", morphing into vowels and phonemes.

Yeah, it's pretty hectic. This is a saturation point of some sort. This must be what happens when synths fly too close to the sun. Here are some sound samples that demonstrate the madness. If you're brave, here's a medley of my FS1R creations spanning 3 months, oldest to newest.

What the hell can you do with this device, then? I tried using the FS1R in a "lead" role for months; carrying the melody, or standing in front of the other instruments, snarling aggressively at the listener. That's not what the FS1R excels at. It sports an impressive collection of waveforms, but compared to other synths I've used, the waves sound soft, and clean. Even with the "skirt" maxed out, the FS1R can't produce a sawtooth wave, or a square wave, or anything big and phat that resonates your rib cage. FM synthesis can sound harsh on other platforms (the Yamaha TX81Z; the Sega Genesis) but the fidelity of the FS1R is apparently too good. You can't make this thing scrape, or scream.

This leaves you with a few options -- you can use it as a "background" instrument, or as a smooth pad. This is where the FS1R shines. It produces excellent textures that liven up a mix if they're used ornamentally. The FS1R could become my "secret weapon", adding that undefinable something to my sound universe. At least, I hope so. FM synthesis is hard to program because you don't really know what will happen when you twist that knob; little tweaks can send a patch spinning. The FS1R constantly surprises me, and that makes it cool. My best sounds come from building a patch using one algorithm (out of 88), and then clicking the other algorithms, arranging the operators into something that I couldn't have premeditated.

It has filters and on-board effects, too. Honestly, I've barely touched these, I'm still internalizing the other stuff. The filter seems unexciting; it's transparent and color-less, although it does offer three lowpass slopes (12, 18 and 24 db/octave), which is nice. The effects include several flavors of chorus & reverb, delays, dynamics processors, and two distortions (although they're soft too, and neuter the sound more than give it teeth).

My wish list for a sequel (the "FS2R"?):

• New modulation types between operators -- ring modulation and hard sync. That way, "the kids" can play it in "the clubs".
• More LFOs. You get 2 per voice, and 1 is reserved for the filter. More are needed!
• Formant sequences should be editable, or better yet, recordable. The manual states that sequences cannot be edited, but of course they can if you're willing to hack it a bit.

Meanwhile, the FS1R will keep me busy with its steep learning curve. At this point, I have rare moments of clarity where I can plan, and (mostly) construct the sound I want. What will I produce after 3 more months? I have no idea, none at all. We shall see.

P.S. Thomas Gruber explains how the FS1R's DSP works, and it's spiffy.

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