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 voltage (current) to ‘code’ audio and control signals. In a musical scale, 1 Volt refers to one octave in the scale. A value of 1V will generate a C2 note on system A, but it can also generate a C0 note on system B. So the note played will differ from system to system.

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 commands the start and length of an action.

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

Filter – Voltage Controlled Filter or VCF
Change the warmth or sharpness of the sound that comes out of that boring buzzing VCO.

Amplifier – 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.

Functions – 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.

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 generators, envelopes, etc.