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Krotos Concept 2

Krotos Concept 2

The latest version of Krotos’ Concept adds granular synthesis and an impressive modulation engine.

You can’t help but be drawn into the modulating centre of Concept 2. The block of colourful, animated waveforms stands very proud from the rest of the interface. You immediately get the impression that you are going to be spending a lot of time in that central section. Version 1 looked slightly odd to me with the grey/white surround but in version 2, with the flick of a switch, you can give it a night‑time look which I feel hangs together so much more pleasingly. The Default preset is cinematically epic and you quickly get the sense that you’re in for a treat...

Easy Synth

The new granular oscillators offer easy controls and variation.The new granular oscillators offer easy controls and variation.

Concept 2 is a relatively straightforward software synthesizer and that’s one of its strengths. As you start to play with it everything unfolds really smoothly. Parameters are familiar and do what they say, and anything that’s being modulated is easy to spot because it’s tied in both colour and movement. I kept expecting to find extra pages of finer synthy detail but everything you need (almost) is right there on the front panel.

At a basic level you have two oscillators and an envelope on the left and the filter and effects on the right. In the middle is the marvellously mad modulation station which we’ll come onto in a minute. The original virtual analogue side of the oscillators remains the same. You can choose two waveforms from the familiar choice of five plus noise, and morph between them with the Blend knob. The result can be detuned, panned, and have its gain set against the second oscillator. FM is provided by an internal sine wave and is probably the easiest and most well‑behaved FM circuit I’ve ever come across. It gives a nice wide range of usable tones from wavefolding to metallic chaos. All the while, the waveform modifications are being displayed and animated in a little window.

Getting Granular

With version 2 they’ve added a granular option to the oscillator and a bucket load of audio files to play with. There are samples from synths, from instruments, drones and plucks, mallets and crashes, there are a whole bunch of Foley environmental sounds, moans, groans and strangled voices. You can import your own samples and add to the already decent library of tones and textures. Without doing any granular shenanigans you can load up a sample and play it as a sound within a single grain of up to 1 second in length. But the shenanigans are the point of this oscillator so let’s get granulising.

In a break from the idea of having everything out on the front panel, the granular parameters are held within three tabs. The Grains tab deals with the start point, the size of the grains, and the rate at which they are generated. This can scan from a slow throb of 0.4Hz to the screechingly metallic sound of 100Hz. Detuning is available along with stereo width and gain. The next tab is called Variation and starts pushing your grains about the place. Spray controls the randomisation of the start point, Density applies randomisation to the size, while Flux messes about with the rate. Drift randomises the pitch, Spread the width and Jitter takes on the level. So, everything you did so nicely in the first tab has an alter ego in the second tab ready to move things about. Tab 3 reveals some extras in a Shape control for softening the front end of the grains and Grain Max for setting an upper limit for grain generation, so your computer doesn’t catch fire. You’ll also find panning and octave controls and the ability to switch in some FM interest.

The granular controls are very clear, and their effect is easy to understand, which is something one doesn’t often say about granular synthesis. As you change samples the granular parameters don’t change; they remain as you’ve set them. While this is good in that it enables you to try out the same ideas on multiple samples it occurs to me that it might be helpful to be able to save samples with their settings as a ‘granular oscillator preset’ for use in other patches. An oscillator library would also give you the chance to sample the range of possibilities within this new oscillator especially if you’re new to granular. The presets do this already but it’s different when you’re focusing in on building your own sounds and ideas within a patch.


The modulator display is colourful and fabulous.The modulator display is colourful and fabulous.So, to the modulation. When you first load up Concept 2 the mid‑section is quite mesmerising. Colourful LFOs scan across the display like a piece of medical monitoring equipment plugged into a hopefully healthy person. If you click on any of the five modulation sections, they roll up to reveal their settings while still showing you a narrow version of what’s going on. From a drop‑down menu you can select which modulator you’d like to use in that section. You can choose between LFO, Envelope, Audio Input, XY Capture, Mod Wheel and the all‑new Advanced Shape. Envelopes and LFOs are easy enough but the others deserve a bit of explanation.

Audio Input lets you take an audio signal from elsewhere in your DAW to modulate parameters. You can either take the amplitude of the input as an envelope or you can switch to pitch mode and detect the pitch, which is then translated as a value for modulation. Most DAWs, like Ableton Live and Reason, can route audio to an instrument but some, like Studio One and FL Studio, do not, so that’s going to be a factor in getting this modulator to work. But in the right DAW you can direct a nice bit of side‑chained audio to your patch in thumping or more creative ways. Simply adding a mic and growling while you play can be a lot of fun.

You can create your own LFO waveform in Advanced Shape.You can create your own LFO waveform in Advanced Shape.XY Capture uses a familiar X/Y pad directed to a couple of parameters but with the added ability to capture the movement. Grab the ball, hit record and your movements can be looped into a fabulous bit of fresh modulation. You can move it forwards, backwards, ping‑pong it, adjust the playback speed or take it manually through its paths. All it lacks is some physics and it would be the Kaoss engine from the Modwave; maybe for version 3?

For the Mod Wheel option, you can set up a completely custom response curve for your MIDI controller’s humble mod wheel, which gives it a surprising amount of new intention.

A similar idea finds its way into the new Advanced Shape option, where it combines a bit of XY Capture with a bit of Mod Wheel to create a custom shape to use as an LFO. Add nodes and curves and draw the path of your modulation and then decide the direction, speed and whether it will run itself or be triggered on every note. It feels like you’ve almost got this already with the other modulators, but the dedicated Advanced Shape really nails the idea of customised modulation.

At the bottom of the four blocks of modulators is a pair of dice called Tweak It. This is a useful randomiser that can be allocated to any of the parameters to throw in some numbers defined by a depth factor. You can have it running just a single control or map it to everything so you can tailor it to exactly what you want to focus on. It’s a really great way to add some variation in all the right places. All it lacks is a way to automate the triggering or to tie it to a note press.

It’s simple, easy and you can see the movement, see the colour, and identify exactly what’s doing what to what. As a modulation system it absolutely shines.

The thing that ties all this modulation lark together is how simple and intuitive it is to allocate modulation to parameters. We’re often faced with complex matrix systems or drop‑down menus of parameter lists but in Concept all you do is drag the label of the parameter on to the modulator. The purpose of their colours suddenly becomes obvious as the depth of modulation appears as a coloured halo around the knob. Pretty much anything that has a label can be dragged to a modulator, including parameters within other modulators. The depth of effect can be set either in the modulator’s expanded settings or by dragging the flag on the halo around the knob. It’s simple, easy and you can see the movement, see the colour, and identify exactly what’s doing what to what. As a modulation system it absolutely shines.

However, as far as I can tell you can only allocate a knob to a single modulator. I couldn’t, for instance, have an LFO slowly scanning the cutoff while also applying an envelope, which is not uncommon in synthesis. The envelope on the left is purely for the amplifier and the fact that there’s no dedicated envelope for the filter does feel like an oversight. You’d have to use up one of your four modulators for that.

Filters & Effects

A good selection of useful and modulatable effects.A good selection of useful and modulatable effects.

On the right‑hand side of the synth is a dedicated filter with seven modes including a rather nice formant one. It has overdrive and a Mix knob so you can blend filtered signal back into the original, which is a nice touch. The overdrive is really nice and gives the filter a sense of depth. The resonance also has a good quality about it that just holds back from self‑oscillation when under pressure.

Underneath are three slots for effects, and you have 10 to choose from including another filter, EQ, compression, saturation, delay, ring modulation and so on. The convolution reverb has picked up over 160 impulse responses and you can import your own. The effects are well thought out. I like how the fuzz of the saturation can be held together by the compressor, how easy and useful the ring modulator is without having to understand anything about ring modulation, and how you can rearrange the order of the effects just by dragging them about. All of their knobs can be dragged into the modulation section, making the effects section part of movement and sound design rather than an afterthought.


Concept 2 is a good sounding software synthesizer that’s great at dealing with waveforms and sublime when encountering granular. It makes many of the tasks effortless while encouraging you to experiment without the danger of getting lost. The use of colour in the modulation section keeps it from getting too complex while pulling off some fabulous feats of interactive movement. It’s refreshingly simple and visually absorbing. While it nails the modulation system it feels like It could do with more slots; four doesn’t quite seem enough, and it’s annoying to lose one in order to envelope the filter. However, the more you fit in the more difficult it becomes to keep it light and accessible. Concept 2 pulls off that balance brilliantly.  


Krotos make a fuss about the depth and range of presets that come with Concept 2 and I have to admit that there are some thrilling sounds in here. Well, you do have contributions from people like Roni Size, Richard Devine and Alessandro Mastroianni. Not just synth and instrument sounds either but environments, soundscapes and cinematic textures that are really inspiring. Krotos’ product line is very much focused on sound design and that shows through the presets and the opportunities for movement and endless variation.


  • Lively front end.
  • Modulation by colour.
  • Range of modulators.
  • Ease of granular synthesis.
  • Clear, resizeable interface.
  • Sounds good.


  • No dedicated filter envelope.
  • You can’t move envelope nodes with the mouse.
  • Can’t combine modulations.
  • Can’t save granular oscillator settings.


Krotos adds an easy‑to‑use granular oscillator to their visually arresting modulation festival, which sounds better than ever while staying accessible and fun to use.


£118.80 including VAT.