Modular Synth – Basics Tutorial03:18


In this tutorial made by The Tuesday Night Machines , we are going to learn what are Control Voltages/CV, Gate Signals, Triggers and MIDI data in a modular synth.

Modular Synth Abbreviations

As a reminder, here is a glossary of most common terms used to describe a modular synthesizer. The entire glossary is available on

CV (Control Voltages)

Control Voltages are used by analog synthesizers to control the oscillators, filters, envelopes generators, LFOs and other components. Originating in modular systems where it was necessary to patch these components together, CV jacks can also be found among hard-wired synthesizers where they were used as an early form of external MIDI-like control for connecting them to other analog devices. CV input and/or output jacks may also be labeled OSC In, Keyboard In, VCO in, or Key Volt.

VCA – Voltage Controlled Amplifier

A device that responds to a change in voltage at its control input by altering the gain of a signal being passed through it.

VCF – Voltage Controlled Filter

A filter whose cutoff frequency can be changed by altering the amount of voltage being sent to its control input.

VCO – Voltage Controlled Oscillator

An oscillating circuit controlled by an alternating analog voltage. This creates the sound in the synthesizer using basic waveform shapes like sine, sawtooth, square, triangle and PWM. Tuning can be unstable, synths can overheat and are often very heavy.


An electronic device which generates a periodic signal of a particular frequency, usually a sine wave, but sometimes a square wave or other waveform. In an analog synthesizer, oscillators typically produce regularly repeating fluctuations in voltage – that is, they oscillate. In digital synthesis, an oscillator more typically plays back a complex waveform by reading the numbers in a wavetable.


In synthesizers, Gate is a clock pulse signal often used to externally control or trigger the note-on, note-off state of an analog synth, to drive the rate of an the LFO or envelope, to start/stop a sequencer or arpeggiator and more. CV and Gate work together to provide the MIDI-like ability to control synths. Gate input and/or output jacks may also be labeled Trig, V-Trig, or S-Trig.


Low Frequency Oscillator. This is a very slow moving oscillator devoted to applications below the audible frequency range for the purpose of adding movement and expression to a synthesizer’s sound. Modulate the oscillator to create vibrato. Modulate the filter to create filter sweeps. Modulate the amp to create tremolo. An LFO can have multiple waveform shapes including square, ramp, sine, triangle, random or more and it’s speed (rate) and onset (delay) are often controllable.

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