GRM Tools Atelier

GRM Tools’ new sound design software is an absolute tour de force!

Groupe de Recherches Musicales (GRM for short) is a French experimental music institution established in the 1950s. It was born from Pierre Schaeffer’s ‘Musique Concrète’ — a groundbreaking approach to composition that treats any recorded sound as raw material to be shaped, rather than notes to be written on a score. Many consider Musique Concrète to be the birth of modern sound design.

GRM released their first plug‑ins (also called GRM Tools) back in 1992, when virtual instruments and effects were still in their infancy. GRM Tools is still going strong more than 30 years later and has become a staple for sound designers. After all this time, it is exciting that a new product has been released.

Atelier is a contemporary continuation of GRM’s experimental ethos and builds on the GRM Tools suite. It’s a multi‑channel, modular, sound‑design sandbox. It comes as a standalone application and as VST3, AU and AAX plug‑ins. At the time of this review, only the Mac version was available. However, GRM tell me that a Windows version should be available by the time you read this review, or shortly after.

Atelier

If you’re familiar with GRM Tools, you’ll instantly see its influence in Atelier. In essence, Atelier is a modular environment where you can add sound sources, effects and modulators, and then connect them with cables. In one sound‑design session, you might create a complex, ever‑morphing drone made with 30 oscillators and a dozen comb filters. The next day, you might be creating your own custom reverb using multi‑layered delays and band‑pass filters. After that, some granular sample mangling, using either your own samples, or by resampling Atelier’s output. You get the idea.

Currently, the Atelier plug‑ins only work as effects or as a standalone application. There is no instrument version, which means there’s currently no way to play Atelier like a synthesizer, even though you can generate sound with sample playback, oscillators, self‑resonating filters and delays. There is some rudimentary MIDI mapping, but not the kind of keyboard playback you might expect from a regular synth. GRM tell me that this is a feature they would like to add in the future.

Despite first appearances, there is simplicity in the UI. This patch is 11 oscillators, going through four comb filters, then into a cluster of 10 delay taps.

Sound Design

You can start, of course, by loading presets. There aren’t many included (just 30 by my count), and the onus is clearly on creating your own, which I wholeheartedly recommend. So, with an empty canvas, you start by adding a processor module. These are sound generators or effects. You might add a Gen module that creates oscillators, followed by a Comb module for comb filtering, and then a Time module for delays. There are eight processor modules to choose from. Apart from the ones I’ve already mentioned, there is Play (for sample recording and playback), Band (for filters), Pitch (for pitch‑shifting), Gain (for amplitude) and Viz (for various handy visualisers).

Processor modules occupy the top two‑thirds of the interface, and you can add as many as you wish. They will always be processed from left to right, in series.

Below the Processor section, in the bottom third of the interface, you can add Modulators. There are just three types, but don’t think this is limited. Each of them is a complex modulation source that covers a wide range. Agitation is capable of all manner of cyclical and random modulation. It’s an LFO on steroids. Peak is more focused on transient shapes: an envelope on steroids. And Control is a macro source: a slider on steroids. Almost anything in Atelier can be modulated. Even randomisers and presets (and each processor module has its own).

LFO. How slow can you go?

Multi‑channel

It’s worth taking a brief detour at this point to explain how Atelier handles voices and channels. It’s quite a unique and clever system. Almost everything related to polyphony, channel management and voices is handled automatically. It’s virtually invisible to the user.

The first thing to note is that each processor module can handle multiple versions of itself. In the Time processor, for example, you can add up to 32 delay taps. The Pitch module can add up to eight pitch‑shifters. Coloured dots represent each processor voice on a graph in the main interface. So in the Delay, each dot represents a unique delay tap with its own settings (delay time, gain, band‑pass filter). Other parameters, such as feedback and dry/wet mix, can be adjusted globally, but modulated per voice. The modulation sources are designed to work in a multi‑channel mode as well. So, one instance of Agitation (the LFO) will modulate all 32 delay taps’ global parameters via a single cable.

Each voice is assigned to a dynamic channel system. Most users will be working in stereo (so two channels), but imagine you’re working in surround. Let’s say seven channels, for the sake of argument.

Almost everything related to polyphony, channel management and voices is handled automatically. It’s virtually invisible to the user.

You add an oscillator. It begins to drone. Because there is only one, it is evenly distributed among all the channels. As soon as you add a second oscillator, the system kicks in and begins distributing the generators around channels. Generator 1 will go to channels 1, 3, 5 and 7. Generator 2 will go to 2, 4 and 6. If you add more generators, the system will distribute them as evenly as it can.

As you add more processors to the chain (filters, delays, etc) each will have different numbers of voices and channels depending on how many dots (delay taps, pitch‑shifters, etc) you add. And the dynamic channel allocation system handles everything. There are options to ‘spread’ individual voices across the channels, and these can, of course, be modulated. The Spread parameter takes a voice and slowly blends it into all other channels.

It is a complex system, but it’s very cleverly presented with the use of colours. Each dot (voice) in the generator is given a unique colour. There is a colour for each output channel. As you ‘spread’ that voice (or all voices), the colour slowly fades to grey. When all colour is gone (just grey), that voice is audible in all channels. Essentially, colour means a voice is panned. No colour means it’s mono (playing in all channels).

It’s a very clever system which I’ve not seen before, and it allows you to have mind‑bogglingly complex patches with a relatively simple interface. Imagine 32 oscillators, each with individual pitches, waveforms and volume. Now imagine the pitch of each oscillator modulated with 32 different waveforms, each at a different speed. And the oscillators going into seven delay lines, which are also being modulated by the same LFO source. In this setup, you only see two Generators (Gen for the oscillators and Time for the delays) and one modulation source (Agitation). The UI is simple, but the complexity of what is really happening is impressive.

To sum this up, part of Atelier’s unique approach to synthesis is to output channels and voices as a multi‑channel system that dynamically adapts to whatever you add to it. As such, it supports just about any crazy multi‑speaker setup you might want to throw at it.

Generators

Let’s take a tour of the Generators. Play is first up. It’s a sampler that can record, play back and loop audio. You can either drag and drop a file or record audio into it. Each voice can have a different pitch, start point and gain. And you can modulate various loop parameters and volume envelopes. You could use it as a simple record‑and‑playback device or a complex granular 16‑voice sound source. As with every generator, you add voices by clicking the graph area. In this case, the graph shows pitch on the vertical axis and time on the horizontal axis. What is lovely is that when you modulate voices, the dots move around the graph to show real‑time values.

Atelier’s Play module can be anything from a simple sample playback device to a complex granular source.

Gen produces up to 16 oscillator voices. Again, you add voices by clicking on the graph, which, in this case, shows frequency on the horizontal axis and volume on the vertical axis. Each oscillator can be a mix of sine, triangle, square and noise, and each of those waveforms has a unique waveshaping option. The oscillators can also react to incoming audio, either ducking or following it (and remember, this is all per channel!).

Comb can produce up to 16 comb filters, each with their own pitch, decay (feedback) and volume. There are additional parameters for damping, overtone warping, phase, and a variable pre‑delay. Here, the graph shows frequency on the horizontal axis and decay on the vertical axis.

Band gives you up to 16 flexible band‑pass filters. Each band has its own centre frequency, width and gain parameters. And there are global parameters for the slope (dB/oct roll‑off), and edge resonance, which is a peak at both edges that GRM call ‘Bump’. The band‑pass filters are flexible enough to be used as high‑ and low‑pass filters or as an EQ. As usual, the graph shows you each voice and its frequency on the X axis, and either gain or width (switchable) on the Y axis.

Pitch is a pitch‑shifter that supports up to eight pitch‑shifting voices. Each voice has an individual delay time, pitch offset and gain. There are global controls for feedback, grain window size and even a clever system which rotates the channels in the feedback path. You can also freeze the state of the pitch‑shifters for some interesting effects.

Time is a delay‑based generator that offers up to 32 delay taps. Each tap (voice) has delay time, gain and band‑pass filter frequency. Several other parameters allow for tape‑based effects, such as tape speed and its pitch response to changes in speed. There is also the same feedback channel rotation option as the Pitch generator.

Gain is a simple gain control, although still multi‑channel. A couple of features elevate it beyond a simple volume slider. Muffle provides some high‑end signal roll‑off, and Distance applies a subtle reverb effect that helps place the sound in a third dimension. Bear in mind that, because these are all multi‑channel and modulatable, you can have channels independently crossfading and moving back and forth in space.

The last generator is called Viz. It offers a suite of multi‑channel visualisation tools, including VU meters, a spectrum analyser, a spectrogram, an oscilloscope, and a correlation meter.

Modulators

The three modulators are highly diverse and offer a wide range of modulation options. Agitation is a cyclical modulator that can handle regular LFO duties but extends far beyond, adding organic randomness and jitter. The key element here is that by connecting Agitation’s output to a parameter on a Generator (or another modulator), you are modulating all the voices in that destination. And with randomness, each voice is modulated differently. You can override this ‘polyadic’ mode so that all destinations move in unison.

Peak offers a similar package, but revolving (literally, if you enable looping) around transient, envelope‑like shapes. There are no familiar ADSR controls, but with a combination of time, repeats, slant, sustain and ease parameters, you can achieve anything from a simple AD envelope to highly complex organic retrigger patterns. Peak can loop itself, or be triggered by other modulation or MIDI mapping. Again, there is a variable randomness, but in this case, it affects which channels Peak will trigger at the destination. For example, if you have 16 oscillators all tuned differently, assign Peak to the gain, and add 50 percent randomness, half of the oscillators will trigger at random. As I’m sure you are beginning to see, organic and random elements are a huge part of Atelier’s approach to sound design.

The final modulator is Control. It adds a single slider with a few parameters that can be used as a macro to set many parameters at once. It can do some wild stuff, like delay its output, and even buffer and mix in past movements. Control is one of the few things in Atelier that isn’t multi‑channel. It’s great for setting up predictable changes in your patch.

Presets & More Randomness

We’re coming to one of my absolute favourite features of Atelier. Each generator can store up to eight presets, each including the number of voices and all their individual parameters. You can then morph between these presets either manually or via modulation. A global morph time parameter controls how quickly presets morph.

The possibilities of this are vast. You might program a bunch of oscillators in Gen to a specific key and scale (did I mention you can quantise all frequency‑based parameters to be chromatically accurate?). If you set up a number of these as presets, all with different scales and frequencies, you can then morph between them.

Each generator also has a small Dice icon in the lower‑right corner. This randomises the generator. You can exclude as many parameters as you like from the randomisation. And there’s a global randomise, which also includes the modulators. That one is wild. But, to tame the crazy, you can set the amount of global randomisation as a percentage. So if you set it to 2 percent, anything you randomise will only deviate from its current value by a small amount. The randomisers also obey the morph time. So they can slowly morph to an entirely different patch. And the best bit? You can modulate the randomiser buttons. Of course you can.

Atelier is fascinating. I promise you that you have never tried anything quite like it.

In Use

Atelier is fascinating. I promise you that you have never tried anything quite like it. At its heart is a philosophy of discovery. It gives you precision and control in all the right places, but also randomness and self‑governed scalability, particularly in voice and channel management, that take the headache out of creating massively complex patches.

The encouragement to perform with Atelier is also charming. The journey is as important as the destination, and several of Atelier’s features encourage this. For example, you can hold down Command whilst dragging a modulation cable to a new destination to set it to zero percent instead of 100 percent, which is handy when playing live. There’s even a built‑in recorder, so there’s no excuse not to capture every sound‑design session, in case you stumble upon gold along the journey.

Atelier’s sonic character is often beguiling and otherworldly, carrying a depth that many modular environments, both software and hardware, could only dream of. You can take it in so many different directions: granular synthesis, design your own non‑linear reverbs, morphing resonators, self‑generating Blade Runner film scores, simple chorus/phaser/flanger effects, techno drones, percussion synthesis, monster vocal processing... I could go on.

I am also struck by the quality and CPU efficiency of the effects. The pitch‑shifters, for example, are as good as any I’ve heard. The comb filters sound wonderful either as delays or Karplus‑Strong models. Almost everything can be modulated at audio rates, or glacially slow. Seriously, you can set an Agitation cycle so slow it will loop once every 300 years. Or so the tooltip informs me. I didn’t have time to confirm.

The UI and attention to detail where it matters are superb. For example, when you modulate a multi‑channel parameter, you get a stream of tiny dots along that parameter’s slider that show you the exact position of each channel’s modulation. Frequency values are always given in Hz, with the note value (eg. 185Hz / F#3). Live waveforms of delays, pitch‑shifters and samplers are superimposed on the graph to show you what each voice is doing. And the use of colour to denote modulation and channels is simple and informative. Atelier is a masterclass in UI design.

If I had to find room for improvement, and I do so under duress because Atelier is utterly brilliant as it is, I would love to see an instrument plug‑in version where MIDI note input could be mapped to any frequency‑based parameter. I would also love to see the ability to save presets for individual generators so that, after meticulous setup, you can reuse those generators in a new patch.

If you consider yourself a sound designer or are curious to see what exemplary software UI and user experience are like in 2026, I highly recommend GRM Tools Atelier. It is a work of art, and often sounds like it.