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You may have seen them on stage or on the internet, modular synthesizers look like a missing panel from a WWII era submarine and are operated by manipulating a grid of knobs through a web of patch cables. They are creators and manipulators of sound that are arranged as a set of modules where each one has a unique job, similar to a mathematical function.

Modular synthesis is seen by some as an overly complex approach to music making, but to others it represents an open playground that’s perfect for experimentation. But before attempting advanced patches it’s important to learn the basic building blocks.

A cv-simple-synth-1VCO (Voltage Controlled Oscillator) is the basic sound source and it’s only job is to output cycles of a simple waveform at an adjustable speed. If you plug a patch cable from a VCO output directly into a speaker, the sound of a pitched tone will come from the speaker at full volume. If you then adjust the oscillator’s frequency knob then you will hear the pitch change accordingly. Often times a VCO gets patched from a keyboard into the VCO’s CV (Control Voltage) input so that each pressed key sets the oscillator frequency to a specific pitch.

There’s no way to adjust the volume on a VCO to have silence between notes, to achieve that you’ll need to plug a patch cable from the VCO out into the audio input of a VCA (Voltage Controlled Amplifier). A VCA module also has only one job, it controls volume, similar to a fader on a mixer. Basic VCAs typically have have only three patch points – a signal input (in this case that comes from the VCO), a signal output, and a CV input. The CV input controls how loud the the volume will be at the output stage.

Those two modules and a CV keyboard (such as a QuNexus) are all you need to create a most basic keyboard patch. To create the patch you’ll need to do the following:

* Patch from the VCO output into the VCA signal input

* Patch from the Keyboard note output into the VCO CV input

* Patch from the VCA output into a speaker

* Patch from the keyboard gate output into the VCA CV input

To better understand the last step, the gate output of a CV Keyboard works like a note on message so whenever a key is pressed, a full voltage signal is sent out it’s output, but when all keys are released, the signal outputs zero voltage. When this is plugged into the VCA CV input, whenever a key is pressed, the VCA outputs full volume, letting the VCO be heard, but when all keys are released the VCA output will be turned all the way down to silence.

The final result yields the behavior where whenever a key is pressed, the specific note is heard and when the key is released there is silence.

In part 2 of this article you will find descriptions of other basic modules and how to use them to build more complex patches.

In the meantime, watch this video by The Tuesday Night Machines where you can learn more about Control Voltage and Gate signals.