The aim is simple enough in theory: we chain modules together to create sounds using electricity. In fact, synthesizers (modular or otherwise) are not acoustic instruments. 

To generate a sound, the basic principle is to use an oscillator, whose job is to produce a basic waveform: a sine wave, a square wave, a sawtooth wave, etc.

This wave is then filtered, amplified, modulated and tortured so that its shape changes from a simple geometry to something more complex. By changing its frequency, we define a note. This modification can be controlled by all sorts of devices, including a keyboard or sequencer.

Let's say it straight away: taking an interest in modular synthesis is not a trivial undertaking.

Modular synthesis requires essential resources: time and money. 

If you only have one or the other of these resources at your disposal, you're bound to be disappointed. With enough money but little time, you won't get much except a fancy collection of modules. With enough time but little money, you risk being quickly out-gunned.

In fact, apart from collecting the essential modules, you also need to plan to have enough of them, as well as being able to add others to continue experimenting. 

Experimentation IS the main advantage of a modular synthesiser. To achieve this, it's quite normal to have a sufficient number of modulation sources and oscillators on hand, unlike an ordinary synthesiser.

The mutliplication of modules, even the most basic, quickly reaches a significant cost. But it is also taking up an increasing amount of space.

Even if the individual modules are small rectangles with little buttons on them, put end to end and you quickly get an object similar in size to an old PC tower. And the weight is also very similar.

So make sure you have enough room to comfortably install your new friend. And remember, the space you occupy will never shrink again. Quite the opposite, in fact.

To avoid losing sight of your objective, it is essential to define and apply a method. It won't prevent you from making mistakes, but it will enable you to limit their number and impact.

For example, you can choose to start with a complete chain offered by a manufacturer and, after a few months, start adding the modules you want. 

A basic piece of advice: add modules very gradually and take the time to explore the new possibilities they offer. 

The idea of starting with a complete chain will allow you to get your bearings fairly quickly, by recreating sounds that you know well. It's instructive and rewarding. Even if instant gratification is not the main goal of modular synthesis, don't lose sight of it. Frustration isn't a good thing either.

Start small, get too big, get small again...

This is what will probably happen to you. And it is quite simple to explain. First, we start with the basic modules. If we like how modular synthesis works, we acquire an increasing number of modules.

The case quickly becomes too small and we have to acquire another one... Now that we have more space, there is a void! The temptation will then be to fill this void with new modules. And it is endless.

Except that we have gone from a compact synthesis chain that fits on a desk to a piece of furniture as such. Experimentation is obviously more interesting with a sufficient number of modules, but do we need such a quantity of possibilities all the time? And it is at this precise moment that the small case that fits on a desk comes back, with the modules that we like and that work well together. This is the synthesis chain that we have spent months or years inventing, that is it. We can finally let it live its life as a full-fledged instrument and... start again with the remaining modules!

This is probably the least exciting part of the modular adventure.

Who can get excited about buying a big empty box with a bathroom spotlight power supply?

However, it is a must, even if you can start with pieces of cardboard or wooden cleats. Acquiring a Eurorack case is a necessary disappointment and it is quite painful since it is expensive.

Depending on the location and the free space you have, do not plan too small. Moreover, look at the "complete kits" of some manufacturers, they offer the basic modules and the case often has empty space.

First burst of excitement!

Whether analog or digital, oscillators produce sound waves. There are all types, from the simplest to the craziest, from Moog copies to real mini-computers that play wavetables or samples.

As always, we'll start with one or two good basics. It's very easy to add more later. Don't be influenced by the "digital" designation of some oscillators: most will be quite capable of producing massive sound.

The VCA (Voltage Controlled Amplifier) ​​is the equivalent of a volume potentiometer capable of being controlled by an external modulation. Most of the time, the VCA is accompanied by an Envelope. This is what allows you to have a snappy sound or, on the contrary, a sound that slowly reaches its maximum and gradually goes down.

There are many types of VCA, but you can definitely start with the most basic, at least to take the time to understand its behavior.

Second dose of excitement!

Everyone loves filters. They contribute enormously to the "color" of the sound, bring life to the whole, also allow to place the instrument in a mix.

Everything exists in Eurorack: replicas of known filters, completely innovative designs, fully digital circuits, crazy combinations... From the simplest LPF with few modulation possibilities, to filter combinations where everything is controllable in CV, it's endless.

Here again, a few good basics will already give you pleasant results. And it is by trying combinations between oscillators and filters that you will find what works best for you.

Modulation modules are as important as the others.

Let's start with the two basic ones: Envelope and LFO.

Two of each is a minimum, especially when it comes to "simple" modulations. A basic envelope has the usual parameters (Attack, Decay, Sustain, Release), that's already interesting, but it's even more so if you can loop it.

Similarly, a basic LFO with a few waveforms, a very wide frequency range and a level control will be useful to start with and will always be useful, even in an advanced configuration.

Accompany these modulations with "Multiples" and you will have enough to start with peace of mind.

There is almost no limit to the complexity of modulations in Eurorack. Thanks to increasingly powerful modules, the use of real miniaturized small computers, mixers, you can obtain completely crazy, long, never repetitive modulations ...

They are difficult to learn, expensive and often bulky (all things considered), but they radically transform a synthesis chain. It is often a good idea to acquire a complex modulation source as the first module to add to your basic chain.

The references are numerous, their operation is sometimes cryptic, but they are very quickly indispensable.

In the Eurorack universe, tell yourself that everything exists or will exist.

There are therefore highly specific, crazy, multi-task, nebulous, unstable modules...

We will find multi-effects, unstable oscillators, electro-acoustic things, sequencers-randomizers based on the cry of seagulls,... everything is possible.

These non-standard modules are as interesting for the seasoned modularist as they are probably to be avoided for the beginner.

Creating a personal and coherent synthesis chain is already a long journey. But keeping an eye on these strange modules is a good idea, at least to understand what they bring and what you could or could not expect from them.