Review – Moodal from tritik

 

And now, for something completely different. Kind of a reverb, kind of a tonal shaper, kind of an extreme sonic mangler. This is Moodal from tritik who previously brought you the delay bargain of 2014, tkDelay. But what the heck IS this thing?

 

by Dave Townsend, Jan. 2016

 

Moodal from tritik is an odd duck. It can radically mangle sound in unexpected ways, e.g. turning a bass guitar into a bell. It can also create colorful reverb-like effects, or it can subtly alter the character of any instrument or voice.

Now, that’s all fine and good, but unless you’re willing to rely entirely on serendipity to accidentally come up with a pleasant sound or two, you’re going to have to first wrap your head around what it actually does and how it does it. That’s what we’re going to do in this article.

 

OK, So What Is It, Really?

When I first read the product announcement for Moodal, my first reaction was “huh?” My second was to visit the tritik website for an explanation. What I found there was less than enlightening: “Moodal is an audio plugin that modelizes objects and spaces to be excited by the sounds you will run through it.” Huh, again.

But being a fan of tritik’s tkDelay plug-in and its developer Charles Gondre, I assumed that whatever Moodal turned out to be, there was a good chance it would be something cool. So I downloaded the demo and experimented. Let’s just say that a few more “huh?” moments followed, as I transformed innocent bass, guitar, string, synth and vocal tracks into unrecognizable roadkill.

So back to the website I went, to dissect the explanations there more closely, starting with Charles’ description: a “resonance engine” consisting of “a thousand resonant filters”.

Correct me if I’m wrong, but I think the first part of that, is totally made-up; there is no such thing as a “resonance engine” in audio. But that’s perfectly OK, because if you’re going to invent something new and unique, what choice do you have but to make up a new term to describe it? So “resonance engine” it is.

“Resonant filter”, on the other hand, that’s a real thing. So let’s start there.

 

Resonant Filters

Synthesists are quite familiar with resonant filters. They exist in real, analog form and they are also mimicked in software emulations.

These are filters that cut off very steeply, so steeply that they cause the filter to oscillate (or “ring”) at the cutoff frequency. This manifests itself aurally as a narrow band of frequencies that keep ringing out even after the input signal has ceased. Kind of like a bell, which keeps making sound long after being struck. Hence the term “ringing”.

Analog oscillators are in fact a type of amplified resonant filter. The difference between a resonant filter and an oscillator is that in a filter the oscillations are dampened rather than being reinforced via regenerative feedback, and therefore do not keep ringing forever. As you reduce the amount of dampening, the ringing lasts longer and longer. Reduce the dampening to a negative value (positive, or regenerative, feedback), and you can even make it go on as long as you like. At that point, you’ve made an oscillator.

This is what occurs in a so-called “self-oscillating resonant filter” (as famously implemented in the Minimoog), meaning a filter that’s encouraged to oscillate. Keep that in mind as you wrap your head around Moodal: how long a resonant filter rings can be anywhere from a few milliseconds to forever, depending on the amount and polarity of feedback.

In between a resonant filter and an oscillator, there is another familiar effect: reverb. Yes, it’s actually related. It, too, utilizes feedback to extend the duration of sounds. The difference is that reverb plugins go to great lengths to spread the bandwidth of the regenerated signal, rather than to just emphasize certain frequencies. Not doing so results in that metallic, recorded-in-a-culvert effect that’s usually (but not always) undesirable.  Moodal’s attitude is that those resonances are a good thing.

 

How Resonance is Used in Moodal

Having trouble making the connection between synth oscillators and an effect plugin like Moodal? Hang in there, it’ll make sense shortly. Some of this will seem a bit, um, academic. But this is going to be new ground for most of us, so we’ve no choice but to get just a little technical. There will be no math, I promise.

Resonant filters only resonate within a narrow band of frequencies. Moog labeled its resonant filter control “Emphasis” on the Minimoog because it emphasizes a specific band of frequencies over others. In a synth or an EQ we’ll usually only have one (maybe two) of these narrow bands to emphasize. But what if you had a whole bunch of them? Like, maybe, a thousand of them?

What if you could take any sound source and make any subset of its composite frequencies ring? Could that be cool, or just annoying? Let’s see.

Here’s a bass guitar, first the original and then run through Moodal.

    Demo Clip

Believe it or not, that bell-like sound is derived entirely from the original signal, without adding any frequencies via synthesis. Everything you hear came from the bass, but with high frequencies extracted and extended by the ringing of a great many (300 in this example) resonant filters.

Time for some pictures. These screenshots were taken using iZotope Insight’s Spectrogram tool. This scrolling graph displays frequency amplitude over time. The test signal I used was a 100ms white noise burst, which looks like this on the spectrogram:


If you’re not accustomed to this type of visual aid, take a minute to familiarize yourself with it. The X axis is time, the Y axis is frequency. White noise consists of all frequencies, so what we see is a wall from top to bottom, showing us that all frequencies are equally represented.

Here’s what the same signal looks like with a bright reverb inserted:

See all that foamy stuff to the right of the main signal? That kinda looks like what reverb sounds like, right? This particular reverb setting is a smooth “bright hall” type, so there are no big lumps in the graph of the reverb tail. The tail is therefore also pretty close to being white noise.

Now let’s see what Moodal does. Here, I’ve exaggerated the effect by using the minimum number of resonant filters and turning up their resonance.

See what happened there? A few of the frequencies (10 of them, to be exact) have been pulled out of the white noise and regenerated so that they keep on ringing long after the original 100ms pulse has stopped.

Here’s what it looks like if we increase the number of filters to 20, and then all the way to 1000:


Notice that as we add more and more filters, we pull out more and more of the frequencies, until at 1,000 filters our picture starts to look a lot like the reverb tail shown previously.

 

So It’s a Reverb, Then?

No. As noted earlier, reverbs make a point of not emphasizing individual frequencies. Moodal’s whole point is emphasizing individual frequencies. In doing so, it acts more like resonant devices such as drums and bells. That’s why the output can sound so radically different from the input.

There are three main parameters you can play with to alter the effect: the relative density, amplitudes and decay times of each resonant frequency. A fourth, spectral distribution, will be discussed later. These parameters are edited via an intuitive graphical user interface that takes about 5 seconds to figure out. Just click on the line to create a node, then drag the line segments up or down.

For example, here we’ve made low frequencies decay faster than high frequencies:

 

 

 

 

Now let’s add more filters to just the midrange frequencies, which we’ll see reflected in the horizontal bars that show filter distribution:

 

 

 

There is also a slider for choosing the total number of filters. Here’s what the difference between 10 and 1000 filters looks like in Moodal’s UI:

 

There are other global controls to further sculpt the sound, such as a master decay (100ms to 10sec), output filter (LP, HP or BP), stereo width and wet/dry faders. These are all pretty much self-explanatory … all but the Spectral Constraint section, which requires a bit of explanation.

 

Spectral Constraints: Inharmicity and Relaxation

The Spectral Constraint panel consists of three controls that set the rules by which Moodal distributes filters’ center frequencies across the spectrum. These rules only apply when the “spectral constraint” on/off button (in the upper-left corner) is activated. It is off by default.

The first control is a rotary slider labeled “f0” that sets the lowest filter frequency. If you want Moodal to not affect low frequencies and only work on the mids and highs, rotate this control clockwise. This also sets a base frequency for calculating the frequencies of all the higher filters. More on that in a moment.

This parameter can be automated. Note that it’s called “baseFreq”, not “f0” in the exposed-parameters list. In fact, all of Moodal’s parameters can be automated for some wild resonant mayhem. Try modulating f0 with an LFO, for example. Unfortunately, the plugin does not include built-in modulation options; you’ll have to do this with automation. Not a showstopper, but I hope Charles considers adding modulation in version 2.0, as that would be a nice enhancement.

The “inharmicity” slider determines the degree to which the filters are tuned to harmonically-interrelated frequencies.  Pushing it to the right will generally result in more bell-like tones, as the filters become less and less harmonically-related.

Harmonics are calculated based on the value set in the rotary knob labeled “f0”. For example, if f0 is set to 400 Hz, the most-significant filters created above it will be multiples of 400Hz. Raise the f0 value and all the resonators shift up, too. Of course, there aren’t 1,000 audible harmonics for 400 Hz, so if you use a large number of filters the majority of them will fall around those harmonic values rather than exactly on them.

Relaxation” determines how strictly to apply the inharmicity parameter. As you turn the relaxation value up (slide to the right), the rules are still applied but become more and more relaxed. Turned all the way up, the inharmicity parameter is effectively defeated.

For example, if the inharmicity control is all the way up and the relaxation control is all the way off, then filters will fall squarely on harmonic frequencies. Start turning up the relaxation and filter frequencies will become more random, while still orbiting around harmonic values and still respecting the f0 setting.

Does all this seem a little academic? Well, yeah. But the plugin’s creator is an academic. A real egghead, in fact. Just google “French National Center for Scientific Research” (Le Centre National de la Recherche Scientifique). That’s the government research institute where Monsieur Gondre did some out-there stuff with audio and DSP.

Check out this video, or his paper on “controlling a nonlinear friction model for evocative sound synthesis”. And you thought that you were seriously into synthesis.

 

How to Get Moodal

Purchase directly from tritik.com:

https://www.tritik.com/products/moodal/

It’ll set you back €75 EUR (about $82 USD at the time of this writing) with free updates for life. It’s available in 32- and 64-bit VST, AU and AAX. If you’re like me and would rather not use an installer, you can download a plain-old zip file with instructions.

A 14-day fully-functional demo is also available.

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