Synthesizer Basics

Even if you’re not considering building your own modular rig, this page could be helpful to understand the basic concepts of a synth and help to determine what you’re looking for.  This will also help you figure out the many virtual synthesizers for your PC or Mac.  My posts will not focus on the technical side too much. Instead, we’ll explore the musical side of modular. But first, we have to create a little glossary with common terminology and identify the essential building blocks that make up a synthesizer.


In the modular world we refer to audio when a frequency enters the ‘audible’ range. Regular frequencies like sine waves create tones, frequency speed creates pitch and shape size affects volume. Irregular shapes create noise, overtones and harmonics. Control signals create short peaks of sound.

CV – Control Voltage
Modular systems use electrical signals to control stuff and to generate sound. In a musical scale, 1 Volt refers to one octave in the scale. A value of 1V will generate a C note. 2V should generate another C, but exactly one octave higher.

We usually can’t hear trigger sounds other than a short tick. Trigger signals are used to command electrical circuits. They can start and stop the playing of notes, trigger a sequencer, define a beat or start a recording. What the trigger does, depends on the module.

Gates are very similar to triggers, with the simple difference that a gate can stay on / high for as long as needed. A trigger can command to open or close a gate. The gate signal controls the start and length of an action. Triggers are often used for drum sounds, but gates can give more expression to a sound by varying the duration.

Building Blocks

The Voltage Controlled Oscillator or VCO
You need a sound source before you can make one.

Voltage Controlled Filter/Folder or VCF
Change the warmth, sharpness, color and timbre of the sound that comes out of that boring buzzing VCO.

The Voltage Controlled Amplifier or VCA
Change the volume of the sound as time passes and bring all the sounds in the system together in a mix.

Function Generators – Some logic that controls the shape, color, movement and volume of the sound.
Common controls are the LFO (low frequency oscillator) that can alter pitch, volume and timbre in a repeating pattern – and the Envelope that works in stages like attack, decay, sustain and release. So looping an envelope basically creates a complex LFO.

Effects – Common effects like the delay, reverb, bitcrusher.

Utilities – Stuff that doesn’t make sounds but helps you control your synthesizer, like the sequencer, clocks, dividers, midi interface, arpeggiator, jogwheel, random stuff generator, precision adder, mults and switches.