How to Use Modular Synthesizers

Intro

Having a synth is cool, but what about creating your synth? The world of modular synthesis can help you achieve exactly that. This guide will shed some light on how to use your modular rig and incorporate it into the modern recording workflow.

What’s a modular synthesizer though?

A modular synthesiser is made of discrete parts (modules) that all interact together to create electronic sounds. Just like in a hardware synth, you can have oscillators, filters, mixers and much more complex units. Most modules carry out a single function in the system, and you can achieve limitless sonic possibilities when modules are combined together. 

A modular synth usually features two types of signal: audio, which is the final output, and CV.

Before diving too deep let’s clear up the jargon and acronyms that we’ll be discussing in this guide. For a more comprehensive guide to synthesizer, terminology checks out our ‘guide to synthesizer terminology’ article here.  

What does CV stand for?

You may have seen this discussed or written on your modular synth. CV stands for control voltage and is an analogue signal. This is the primary way information is sent between modules. Think of it as the analogue equivalent of MIDI. Just like it is possible to send MIDI information in and out of our computers, it is also possible to send CV using specific hardware and software. We’ll discuss this in more detail later in the guide.

What is a VCO, VCA, and VCF?

These terms stand for Voltage Controlled Oscillator, Voltage Controlled Amplifier, and Voltage Controlled Filter respectively. These are devices that use CV to modulate or set certain parameters such as the frequency of an oscillator, the volume of an amplifier, or the resonance of a filter.

We can say that VCO determines the shape of your sound, VCF defines its ‘voice’ and VCA controls its volume. 

Bonus: you might have noticed there are also semi-modular synths. Put simply, they combine hardware synths with a patch bay. You can use your synth as it is, and tweak the sound with the available controls, such as a filter cutoff and resonance and so on, or you can start using patch cables to bypass existing connections. This way you’ll be able to modulate parameters in new, creative ways and shape a unique soundscape!

Semi-modular can be a great way to get more into modular synthesis via a guided path. A great option for beginners is Korg’s Volca Modular, a compact but powerful box where you can patch up to eight modules in the size of a VHS! Behringer’s flagship Neutron has a patch bay with a 32-in/24-out matrix if you want something more sophisticated. With two 3340 oscillators, two analogue VCAs, filters, BBD delay and more it’s going to be your travel buddy into the world of patches. It’s also Eurorack ready to fit swiftly into your system. If you crave that vintage analogue sound, Moog’s Mother 32 is a gem for all you semi-modular lovers out there! It also includes a sequencer for creative melodies and drum patterns. 

What are the essential modules I need to have?

Exploring modular synthesis is a lifelong journey and has no predetermined path. You can experiment and choose the modules you like and be reassured you’ll never have the same result as someone else! There are, however, a few fundamental modules:

• Source modules: they are the source of your sound. They usually only have an audio output. They can be VCOs or Noise generators, as well as LFOs and Envelope generators. 
• Modulation modules: they shape the sound. The basic one is the VCF to shape the tone and VCA for the volume, then you can add delays, ring mods, reverbs and much more. 
• Logic modules: they give information about clock timing. They are often used to activate different gates and triggers to achieve interesting sound patterns.

VCO Modules

What if I want to control my modular from my keyboard or my DAW?

Think of it like two people who speak different languages. An interpreter can be the point of mediation to solve the issue. In the same way, modular synths speak CV, while other pieces of gear and software speak MIDI. A MIDI-to-CV converter is essential to make the signals coming from your laptop or keyboard turn into a message that your modular can decipher. It sends Pitch CV and Gate information to your modular so it sounds exactly as you want.

How do I create a modular synth patch?

Unlike hardware synths, the modules in your modular communicate and work only if you make physical connections. This is referred to as patching and consists of uniting modules’ inputs and outputs via patch cables.

Creating your first patch may be a little daunting if it’s your first foray into modular synthesizers. It’s a good idea to outline the plan for the signal flow before you get started, so you don’t feel lost under a mess of patch cables!

There are millions of ways to create a patch, which is why people love modular synths. But ultimately it depends on what modules you have available and how creative you’re feeling. Here’s a simple example of signal flow.

The VCO creates a waveform, the VCA controls the amplitude of that waveform, and the mixer adjusts that signal to line level and sends it out ready to be recorded.

Excellent, so we can create a continuous sound, now what? Let’s look at one more example but this time with a few more modules to give us greater control.

In this example, we’ve added a sequencer, envelope, and VCF. The sequencer sends pitch information to the VCO, and gate information to the VCA via the envelope which shapes the character and length of the note. If you’ve heard of the term ADSR, this is what the envelope achieves, essentially telling the VCA how to open and close for each note. The pitch information from the VCO feeds the VCF before the VCA. A VCF is used to tonally shape the sound, somewhat similar to an equaliser on a hi-fi or guitar amp.

These two patches are some simple examples, and ultimately there is no right or wrong way to create a patch as long as you like the end result, so experiment!

If you need a visual guide to get going with your modular system, we crafted a unique tutorial to help you take your first steps, from setting up your modules to creating your first patch:

How do I record my synthesizer and sync it to my DAW?

So, you’ve created the perfect patch worthy of the next Brian Eno album, but how do you sync and record it into your project?

There are multiple ways to integrate and synchronise a synth with a DAW setup. The best one for you will depend on what you want to achieve and your end goal. First of all, gear up with a first-class audio interface, like Apollo Twin by UAD, Focusrite 4i2 or Apogee Duet 3. You can also consider using a mixer like the Allen and Heath ZED14 or the Yamaha MG12 if you’re wanting a more advanced setup. 

Let’s look at probably the most common and easiest way. Treat your synth like any other instrument and patch from your master output into your recording interface, set the gain, and hit record. Working this way we are treating the DAW as an audio recorder, or a tape machine. Once we have the sound or sequence recorded it is possible to edit, cut, move, repeat, and sample it in the DAW if desired. The downside to this approach is that we can’t tempo synchronise the DAW and modular except for doing it manually during the performance or via editing once we have captured the audio.

An easy way to bypass this problem is to enter a MIDI to CV converter module into your modular system. Using one of these modules in your setup allows you to control CV with MIDI data from external devices such as MIDI controllers/keyboards or your DAW. For example, it is possible to modulate the resonance of a VCF using automation in your DAW, start and stop your sequencer at a specific point in the project, or synchronise the frequency of an LFO to match your project tempo. One downside of MIDI to CV is the limitation of MIDI resolution to 128 values. You can imagine this as 128 individual steps from the minimum value of a parameter to the maximum value. Some people feel this resolution isn’t high enough for parameters such as the frequency on a filter and can hear the steps when the frequency is swept. This is where the analogue world has the advantage of practically infinite resolution between two voltages.

How about a DC-coupled interface?

Some keen readers may be thinking, “my recording interface outputs analogue signals like the ones that go to my speakers… why can’t I use those to control CV on my modular synth?”, and they would be correct to think that! Some DAWs, notably Ableton Live, have created CV Tools that allow you to send CV from your DAW to your modular synth, or any CV compatible hardware via a DC-coupled audio interface. This may sound confusing but a DC-coupled audio interface is just one that allows you to send DC voltages in and out where most audio interfaces try to block this. The recording interfaces that are DC-coupled actively use this as a selling point and you can see the ones we stock here:

DC-coupled Audio Interfaces

No matter your sync approach, the end goal is to get an audio signal from your modular into your recording interface. Modular setups generally work with audio signals that are a lot louder than a typical keyboard or guitar output and may distort the preamps on your interface, so it is advised to pad down the end of your modular chain with a mixer that can output the signal at line level. Products such as the Behringer 305 can achieve this and fit neatly in a Eurorack setup.

How to build your own modular synth

The most exciting part of a modular synthesiser is that it’s completely customisable. You can mix and match all types of modules from different brands, to create a sound that is unique to you. If you want to build your own modular synth, at Andertons we stock everything you need to get started!

CASE & POWER SUPPLY

First and foremost you need a case to host your modules. The things you’ll want to look at are its HP (horizontal pitch) and if it’s powered. HP is the measuring unit for modules. The more HPs, the more modules you’ll be able to fit into that case. For example, Arturia’s Rackbrute 6U Eurorack case can connect up to 32 modules. If your case is already powered, then you’re all good to go. Otherwise, you need to get a power supply module like Tiptop Audio’s μZEUS. 

Modular Synth Cases

VCA

A VCA is essential to control the volume of your oscillator and is often the unsung backbone of a modular system. Go for one like Studio Electronics’ Modstar VCA Amp, which allows you to control the volume in two ways/stages at once!

FILTER

VCFs shape the oscillating sound. A very basic filter will subtract harmonies from your sound, formally known as a low pass filter. A more advanced option is Roland’s System 500-VCF 521 that includes 2 low pass filters and 1 high pass filter.

EFFECTS

Effects are a chapter of their own. You can really get crazy with your effects, from granulators to reverbs to delays. This is where you can really create your personal synth and ‘voices’ never heard before. 

Some of our favourites are Earthquaker’s Afterneath Reverberation machine, Eventide EuroDDL Eurorack Delay Module and Dreadbox Dystopia Noise / Crush / Filter. 

Eurorack Effects Modules

PATCH CABLES

As we said before, patch cables are essential to make the connections between modules and have it sound as you want. You can find them in all colours and sizes, here are some of the best you can find at Andertons:

Conclusion

This is just an insight into modular synthesis, but it really is a universe to discover and shape! If you want to know more, you can stick around and check out our guides:

• Synth 101: a Guide to Synth Terminology 
• A Guide To Modular Synths
• Desktop Synth vs Modular Synth
• The Best 5 Guitar Effects Pedals for Synths (2021)