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Beginners Tutorial for Modular Synthesizers

A crash course in modular synthesizers.

What is a Synthesizer

Modular Synthesizer

A synthesizer is a machine that uses electronic circuits to create signals to produce sound. The sounds can emulate existing mechanical instruments like horns, drums and strings, and also to create sounds that don't occur in nature and that you've never imagined. A synthesizer can be almost any size or shape, it might be controlled by a keyboard or by knobs or some other type of controller.

Analog and Digital

Analog and digital waveform

Analog circuits create continuously variable waveforms that sound smooth and natural. The first synthesizers were analog and large. Moog, Buchla, ARP and others produced the first analog synths in the 1960s-1980s.

Digital circuits create waveforms from numbers in a digital circuit or computer. Even though digital waveforms are created with tiny discrete voltage steps as opposed to continuously changing voltages, they can emulate most sounds adequately for the human ear. But many can still hear the difference. Digital synths typically have preset storage and are small, but are difficult to program.

Types of Synthesis

Analog and digital synth

Analog synthesizers typically use subtractive synthesis to produce sounds. Subtractive synthesis starts with one or more oscillators to produce waveforms, then uses filters to subtract harmonics. That's subtractive synthesis.

Digital synthesizers typically use FM (Frequency Modulation) or sampling or some other strategy to build the sound. Digital methods are typically more difficult to program than a subtractive synth.


massive patching

In a patchable modular synthesizer, function blocks are independent from one another and mounted on panels that can be moved around. Sort of like guitar pedals. It's up to the users to patch the modules together as they like. This is different than a normalized synthesizer where the functions are hard-wired together and the user just changes parameters. Patchable modular synths are more complex to operate but give you infinite options.


Modular patchable synthesizers are typically monophonic meaning only one note plays at a time. This might sound limiting at first, but a modular's sound is very big and can be comprised of many oscillators and filters and changing effects. It is possible to do some polyphonic patching with a modular but that's not its primary purpose.

Voltage Control

Synth patch

Voltage control is a key concept in modular analog synthesis. It's simple but it must be learned and fully appreciated. Voltage control gives the modular its flexibility and power. You must think in terms of voltage control to use a synthesizer. It's fun and mind-expanding.

Voltage control simply means that a voltage signal can change a parameter on a module the same way a knob can. This allows one module to control parameters of another by patching them together.

For example, to add vibrato, patch a one slow oscillator's sine wave output to another oscillator's frequency control input. The slow oscillator will control the other oscillator's frequency producing vibrato. That's voltage control. Sometimes called VC.

Pitch and Gate Signals

Pitch and gate signals

In a modular synth, a pitch voltage controls oscillator's pitch. The most popular standard for pitch voltage is 1-volt-per octave (1V/Oct). For example, on a keyboard, the low C would be zero volts, the next C up would be 1 volt, the next C would be 2 volts, and so on. Oscillators are designed to track this voltage to produce the correct pitch. A pitch voltage can come from any source - a keyboard, another module, etc. That's the freedom of voltage control.

Gates are On/Off signals. They're mostly used to turn things on and off such as sequencers or envelope generators. Pressing a key on the keyboard generates a pitch voltage and also a gate signal indicating that the key is pressed. Both pitch and gate signals use the same type of connector and the same type of patch cables.


Q109 Envelope Generator Module

An envelope is a voltage signal that changes over time and is created by an envelope generator (EG) module. Many sounds need to change over time and we use the voltage from envelope generators to control parameters. The EG has controls that set the timing of the output envelope voltage over time. EGs are normally triggered by a Gate signal from a keyboard, but because this is a modular, that gate signal can come from many other sources such as an oscillator or a sequencer.

Voltages - Attenuating, Inverting, Mixing


Since voltages can control parameters, it makes sense to offer ways to modify that voltage for different effects. Control voltages can be reduced in strength (attenuation) to reduce their effect. They can be increased in strength (amplified) to increase their effect. And they can be inverted to reverse their effect. Many modules that receive control voltages have knobs to attenuate and amplify them. Some also are able to invert the signal too, all on the same knob. That's called a reversible attenuator.

The Basic Patch

Basic Synthesizer Patch Synth patch

Here's a quick patch to get you going. It might look complicated at first, but once you see what each module does, it's simple and logical. The signal chain goes from left to right. MIDI provides the notes to the MIDI interface which produces pitch and gate signals. The pitch signal controls the Q106 Oscillator and the ramp waveform from the oscillator goes into the Q107 filter. The filter changes harmonics of the ramp wave and the filtered output goes on to the Q108 Amplifier where the signals amplitude is controlled. Since gate needs to go to two places, it's patched through a Q124 Multiple which is just a patch bay. The gates then go to two Q109 envelope generators. One EG controls the filter and one controls the amplitude.


Q960 Sequencer Module

A sequencer is simply a module that produces a sequence of control voltages and gates that can be used to control modules. Knobs for each stage determine the voltage at the output. Often they are used to create a melody of notes by driving oscillators, but sequencers can also be used as an arpeggiator following keyboard notes, or to create bizarre waveforms.

The Freedom to Patch Anywhere

massive patching

In a modular synthesizer, you can patch anything to anywhere. Don't worry, nothing will break if you do it wrong. In fact, there is no wrong, but not everything you patch will be musically useful, that's up to you to decide. Real-time hands-on experimentation is the greatest part about modulars. It will change your mind and your soul.

Buying a System

One thing to remember when buying a modular synth is that you can add on and change things around any time. You can start small and build up to a bigger system.

Box11 Modular Synthesizer Systems
First browse our systems pages and select a cabinet style. Do you want a solid walnut studio cabinet, a vinyl-covered portable cabinet, rack mount, or maybe a Box11 style? Within our pre-configured system offerings, you'll most likely find something that is what you want, or at least very close.

Box11 Modular Synthesizer Controllers
Once you decide on a system, look at the pre-configured controller bundles. Like for systems, there's a lot of options, but one of our bundles will likely be very close to what you're looking for. If you want to use your computer or an existing controller for your modular system, no problem, just make sure you have a Q174 MIDI Interface module to produce pitch/gate signals if you're using MIDI.

The process starts with you filling out the quote form. We will send you a formal quotation with prices, shipping details, and payment instructions. You make payment and we ship your products. The process works good and our customer service is unsurpassed.

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