Review – Fission from Eventide


Eventide has an innovative new effect, Fission.  It’s one of those “why didn’t somebody think of this a long time ago?” type plug-ins.  Why indeed?


by David Baer, May 2017


Transient Designers

Eventide has introduced a marvelous new effect called Fission that is, at least at the moment, quite unique.  It combines the front-end capabilities of a transient designer (or envelope shaper, if you prefer) with a selection of effects that can act independently on the two parts of a signal (i.e., the transient and non-transient parts).  Let me hasten to point out that Eventide would probably want to immediately assert that Fission is not just another transient designer, but let’s defer that discussion for just a moment.

Musical audio signals, both acoustically and electronically produced, often begin with a burst of energy that is followed by a longer sustained or slowly decaying segment.  Percussion/drum instrument sounds certainly have this characteristic.  So do any tuned instruments played by striking or plucking a resonant object.  Transient designer plug-ins have been with us for quite some time.  They separate the initial burst (almost always referred to as the transient) from what follows (what follows being called names like “the sustain” or “the tonal” portion of the signal).  Transient designers are effects that allow independent level adjustments to be made to the two segments of the signal.

So, they can have great utility in mixing.  Need to make that snare sound snappier?  Easy: accentuate the transient and suppress the sustain portion.  Want to make an acoustic guitar “sing” a little more prominently?  Do just the opposite.  These are very useful devices and many (but currently not all) DAWs come bundled with one as a stock tool.

But they mostly just do two things: allow gain adjustments to the transient portion and gain adjustments to the sustain portion of a signal.  Here’s where Fission comes in with an innovative and exciting take on this basic concept.  In addition to gain adjustment, why not be able to send the separated signals through separate effects before remixing them on the way out.  Brilliant!  But why didn’t somebody think of this maybe a week after the first transient designer became available?

That said, Fission isn’t a game changer.  This is something that could always have been done with two instances of a transient designer and some basic sends.  What Fission brings is the ability to do this with considerable ease.  Creative experimentation is so little work it becomes not just rewarding but also fun.

Before we continue, let’s dispense with some fundamentals.  Fission is available in all standard formats: VST, AU and AAX, both 32-bit and 64-bit compatible.  Authorization is via a free iLok account; use of an iLok dongle is an option but not required.  The list price is $179 USD but at the time this is being written an introductory price of $97 USD is in effect.  Eventide has offered substantial discounts during occasional sales in the recent past, so patience in waiting for a good price may be well-rewarded.


What’s a Transient Anyway?

With the preliminaries out of the way, let’s ask the obvious: what constitutes a transient?  Answering this will shortly lead us to the subject of “Structural Effects”, Eventide’s technological solution to the problem of separating the transient from the rest of the signal.  But back to the question: what is a transient in the first place?

In a real-life sound, like a drumstick striking a drum or a finger plucking a harp string, we intuitively know what the transient is.  The transient has a very fast attack and a fairly fast decay down to the starting sustain level, a level that is normally considerably lower than the peak of the attack.  The sustain portion of the signal usually also decays but does so at a somewhat slower rate than the transient decay.

So, how does a software plug-in recognize a transient?  A naïve answer might be: use an envelope follower like a compressor does, with the attack parameter set to an appropriate time interval.  But an envelope follower requires a threshold level to be established which might leave some quieter signals with legitimate transients undetected.  We want to detect anything with a sharp attack and fast decay irrespective of the level of the attack peak.

Well, it’s fairly easy for a digital process to look for a rapid increase in signal level, so that part should not be a problem.  But do we also require a fast decay to immediately follow?  What about an organ-like signal: fast attack but no decay at all?  Without a look-ahead, the detection processing cannot even know if a rapid fall to a sustain level is coming or not.  These are the sort of things with which the engineer creating a transient designer must contend.

In the case of Fission, Eventide claims the answer lies with Structural Effects.  I’ll let Eventide’s own promotional words from their website explain:

Eventide’s patent-pending technology, Structural Effects, does something new. It separates a sound into its transient (impact/unpredictable/jagged) and tonal (sustaining/stable/smooth) parts more effectively and accurately than previous methods.  …

First the waveform is divided into frames of ~40ms and is analyzed to find stable and/or predictable patterns. Stable sound components are then classified as tonal elements of the sound. There can be subtle or radical changes from frame to frame, but as long as those changes are predictable in the short term we choose to classify those elements as tonal. For instance, the decay of a note on a piano is a fairly predictable event even though the harmonics may shift slowly and the exact decay envelope is unknown. By analyzing individual frames in the context of the overall sound we are able to classify elements as tonal even as they vary over time.

Once the analysis has identified the portion of the sound that it ‘determines’ to be tonal, it then gracefully eliminates those portions leaving only transients. In a sense, the method ‘sifts’ the audio, separating the smooth gold (tonal) from the jagged sand (transient). The result is two completely separate, yet recombinable, streams of audio: a tonal stream and a transient stream.


The Structural Split Module


If you’re wondering where all this is going, rest assured that we’re almost there.  The above screenshot shows the portion of the Fission UI that is used to set up the transient/tonal split.  From here on we’ll use Eventide’s term for the non-transient portion of a signal: the “tonal” part. 

On the left are four controls that dictate how the transient/tonal separation is accomplished.  To the right of these controls is a graphic representation of the signals coming out of the Structural Split processing (before any level adjustments and/or FX are applied).  The top line shows the transient and the bottom the tonal parts of the signal, with the full original signal depicted in gray in both cases.  The transient and tonal lines actually depict left and right signals individually – left is above the center line and right is below it.

Let’s start with the Trans Decay control which can be thought of as a cross-fade control (the manual goes into more detail, but we’ll keep it simple for now).  With all other controls set to their defaults, I set up a test to see how the decay control affected the processing.  The test signal to the right was used: a simple saw wave at moderately high frequency.  The envelope used the fastest possible attack, a hold of about 200 ms, a decay to -6 dB with the fastest possible time, a sustain, and finally a release with fastest possible time.  Why this strange shape?  Look at the transient signals coming out of the separation process using Trans Decay values of 0, 50 and 100 respectively.  Notice in particular that the transient detection did not just regard the leading attack as transient activity.  The sharp decline after the hold and the release also was deemed to have transient characteristics as well.



Just for completeness, below is an image showing the corresponding tonal parts of the signal for the three tonal signals we just examined.


The moral of this story, to me anyway, is that it is fairly important to really understand what your transient designer tool is up to.  It’s highly enlightening to run a test like this using a variety of transient designer tools.  There is a surprising divergence in what they do on identical input signals.

Now, it’s true that most musical signals will not have sharp declines in signal level after the initial transient.  But if they do and you’re applying a transient separation process, you may get unanticipated results if you don’t understand the behavior of a specific tool.  At least that seems to be the case with Fission.

But let’s move on to the other Structural Split controls, starting with Smoothing.  Rather than try to restate what the manual says, let me just repeat it here verbatum:  The Smoothing control is a fine tuning control used to slow down the fastest transitions (in time and frequency) in both directions between Transient and Tonal. Basically, this controls how fast a piece of Transient or Tonal audio can switch to the other stream. This is primarily used to smooth out any artifacts that you may encounter with difficult source signals.

If you find the function of the Smoothing control vs. the function of the Transient Decay control a tad confusing at first, welcome to the club.  But a picture will hopefully provide a little enlightenment.  In the image to the right, we see a portion of the Fission graphic display with the Smoothing control set to 0, 50 and 100 respectively (the Trans Decay control set to its default of 20 for this example).





The Focus control looks like a simple balance-type control, which mainly it is.  The documentation makes some references to frequency-dependent operation: the real separation magic occurs in the middle settings, where Focus sets the main transition region or decision point where audio splits (in time and frequency) into the separate Transient and Tonal streams.  But I suggest you don’t overthink it – just use this control to emphasize either transient or tonal and you’ll probably get very close to what you are expecting.  The image right shows five positions from all tonal to all transient, and it’s just what you’d expect.


The final control in this area is the Source Type, the choices of which are shown to the right.  The manual is not especially forthcoming about what affect this setting actually has on the sound.  The differences between the settings are actually quite subtle, but setting up a null test proves that something is in fact going on, even if you can’t hear any difference when changing the selection.  It’s probably best to just pick the choice closest to whatever is on the track and not worry any further about it.

One final point about Structural Split: you can turn it off entirely.  When doing so, Fission becomes a dual, parallel effect module, with the Focus control controlling the audio levels to the partner effects.




The Effects

I do not think we need to spend any amount of time digging deeply into the effect offerings in Fission.  If you don’t know what a delay or chorus effect does and how to control their operation, you’re probably not going to stray far from just using presets anyway.  But we will take a quick tour of the possibilities.  All these effects are quite thoroughly explained in the manual, so refer to that if curiosity compels.

To begin with, there are two effect slots, one for transient and one for tonal.  Either can be turned off entirely, but if on, one (and only one) of the several effects is selected.  For transient, the choices are: delay, dynamics (a compressor), gate plus EQ, phaser, reverb and tap delay.  They are all fairly basic but quite capable (Eventide does know a thing or two about high-quality audio effects, after all).

Below are seen the respective panels of each of the transient effects.

For tonal effects, we have a different set of choices: chorus, compressor, delay, EQ, pitch controller (more momentarily), reverb and tremolo.  You may note that the transient dynamics module is called “Dynamics” and the tonal one “Compressor” and yet their interfaces are identical.  Well, not quite.  The range of the ratio control in the former allows it to be an expander or compressor, while the tonal dynamics module can only compress.

The only effect that’s a little off the beaten path is Pitch.  This allows the signal to be shifted in pitch up to plus or minus one octave.  A second and third voice can be added if desired.  A fine tune control affects all voices.  This module can be put to good use for both unpitched drum/percussion and pitched musical sound alteration.


Here are the panels for the tonal effects:


Factory Content

Eventide has provided a wealth of great presets in the factory content.  These are organized into the categories: Instruments, Effects, Mixing and Artists.  There are nearly 450 presets in all, about half of them in the Artists category.  The factory content is comprised of all manner of both workaday and inventive/creative concoctions that amply cover the considerable range of possibilities that Fission offers.

Instrument subcategories are drums/percussion, beats, guitar, bass, keys, synths, vocals, horns/winds and strings.  Effect subcategories are structural/split, multiFX, delay, reverb, pitch, modulation and tremolo.  Mixing is comprised of just three subcategories: EQ, dynamics and multi.

The more creative fare is to be found in the Artists category with 22 contributing sound designers supplying much variety.  If one takes the time to audition even a fraction of all these presets, it quickly becomes evident what a considerable diversity of sound alteration options is offered by Fission.


Is Fission for You?

As far as I know, Fission is the only effect module on the market that does what it does, at least as a self-contained plug-in.  You could duplicate its function to some extent with the transient designer included with your DAW (assuming there is one) and an investment of time to set up the channel configuration to accomplish this.  So if you are longing for this capability but are budget-constrained, you have an alternative.

But rolling your own is a whole lot more work than just using Fission.  Plus, you will miss out on one of Fission’s greatest assets, the factory content.  As stated earlier, this covers a vast area of sound possibilities and offers some wonderfully inventive presets for taking your audio in unexpected directions.  So, if it’s in your budget, immediately or when a sale comes along, I would heartily recommend checking out this dandy piece of virtual gear.  To that end, there are some very good demo videos available on Eventide’s web site (URL just below).

I have to believe that now the idea is out there, Fission will have some competition at some point.  To my mind, this is just too good an idea for there not to be imitators emerging rather soon.  To that end, I do hope Eventide has got a version 2 on the drawing boards.  I think there’s one way that this great effect could be made considerably better: allowing multiple effect modules to be chained.  One could easily see the benefit in combining a delay or chorus with a reverb on the tonal side of things, as one example.  Also, why limit the included effects to just transient or just tonal?  Why not make the phasor available on the tonal part as well as on the transient, for instance?

Watch this space – future developments may prove to be quite interesting.

Fission is available through any number of sound software retailers.  To purchase directly or to just find out more, go here:





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