A standard equally tempered scale for controlling the pitch of the oscillators of analog synthesizers. Most of the Eurorack modules' inputs are manufactured according to this standard. The other, less frequent standard is called Hz/V.

AC Coupled

A kind of input, that can only pass on AC (that is, in our case, audio) signals.


An attenuator is a tool that reduces the CV or audio signal's strength at the input.


An attenuverter is a special kind of attenuator, that is not only capable of reducing the input signal's strength to zero, but it is also capable of bipolar (that is, being in the range of both positive and negative directions) attenuation.


Amplitude modulation. The waveform is modulated by another source not at its frequency, but at its strength or amplitude.


Bucket brigade delay. This unit is created by daisy-chainging plenty of basic digital units. It is essentially the forerunner of modern-day digital delays, and it has a "lo-fi" sound compared to their modern heirs. However, it is still being widely used to generate rough flanging/chorus type of sounds or tape echo simulation.

Bi Polar

Any modulation can be called bi-polar, if it contains positive and negative voltages.

Bus Board

The modules are connected to bus boards so that they can be powered or receive gate or modulation signals. Recently TipTop Audio has started developing modules that are capable of transmitting audio signals through the bus board.


A clock signal. Many modulation sources (a sequencer, LFO, etc.) that function on a periodic basis can usually accept a clock signal on which its timing (hence its modulation) will be changing accordingly, e.g. in a synchronized manner. A division or multiplication of a clock signal can be used to generate simple rhythmic patterns.

Clock Divider /Clock Multiplier

The name of certain modules that can divide or multiply a clock signal (which is usually a rectangle wave with appropriate frequency).


Control Voltage - modular synthesizers can not only be controlled manually by means of knobs, but also by voltages transmitted through patch cables. CV signals can contain positive and negative voltages too.

DC Coupled

If an input is DC-coupled, then it can process / pass through audio and CV signals as well.

Envelope Generator, ADSR

Also called function Generator. It is a time-based modulation source that strengthens and weakens continuous audio or CV signals in seperate phases. A standard envelope generator usually has 5 parameters: attack (the phase which reaches the top of the signal strength),  decay (the phase until the point that it gets sustained at its value by the next phase), sustain (the amount of signal strenth that is kept after the decay, so this is not a time based parameter), and release (the final decay phase after the keyboard/gate signal that started the envelope is turned off). Typically, an envelope generator is used to change / modulate an amplifier (VCA), an oscillator (VCO) or a filter (VCF).


Frequency modulation. The waveform is being modulated at its frequency by another modulation source.


A CV signal that can be turned on and off. Think about it as your modular synthesizer's universal "key" (from a keyboard).


A tuning standard that represents an octave's range by doubling the voltage. This standard is applied in Korg and Yamaha analog synths. The other, more common standard is 1V/octave.


The inverter units on the modules always send the input voltage with the opposite polarity to their output.


In many cases you can find a jumper on the printed circuit board (PCB) of the module (they are mostly used instead of a panel switch). By means of a jumper, changes can be applied to the functions of the module.


A Low Frequency Oscillator that is usually applied as a modulation source. Some LFO's can be used in the audio range as well.

Low Pass Gate

A combinatory sound processing tool that consists of a lowpass filter and an amplifier. In combined mode, the filter's cutoff can be dependent on the amplitude of the input signal.


A musical or other kind of parameter's dynamic change in time.


A tool that multiplies a signal on 1 or more outputs, so that the signal can be routed elsewhere too in the modular system.


A noise generator. In many cases, the noise can be used as an audio or CV signal as well.

If an input and/or output on a module is normalled, it means that the signal on the input/output becomes available on the other inputs/outputs as well.

An input signal can be offset to positive or negative direction (polarity).

A modulation tool. It takes an input CV signal and turns them into elements of a corresponding (usually) equally tempered scale.

Ribbon Cable
The modules are connected to the bus board or their extension modules via a ribbon cable to get power, gate signals or other kind of audio or modulation information.

A modular synth patch is regarded as a complete series of musical events that are created by one or more modules' interaction and use.

This special filter creates comb-shaped curves in the audio spectrum. It is sometimes referred to as an "allpass" filter.

The rectangle/square output of an oscillator being modulated at its width parameter (pulse width modulation).

The Ring Modulation is a sound processing tool or effect. The two input signals' sum and difference frequencies go to the output. This way, the ring modulator creates metallic, ringing tones.  

A digital sound processing tool. An "sampled" input signal is being "held" until the next trigger signal arrives on the other trigger input - this way, stepped or "staircase"-like signals can be created.  

Self Oscillation
Some of the filter designs allow that their resonance parameter (which is basically a feedback into the circuit's audio input) to go into self-oscillation. In many cases, a sinewave (or sinewave-like waveform) is generated with the input audio signal at the output.  

A sound processing tool. It makes more edgy or sharp input signals (e.g. voltages coming from a step sequencer) more rounded. Typically, it is applied as a portamento effect, however some slew modules can be used as envelope generators as well.

Step Sequencer
The step sequencer works with an internal or external clock signal. The sequencer sends out step-divided signals (usually 8 or 16 steps) in that clock-based tempo, and the output values can be changed per step.

Short Circuit Trigger or Negative Trigger. Mostly, Moog and Yamaha analog synths use that trigger standard, which means they cannot be efficiently used with a standard trigger signal.


Many modules' functions can not only be accessed via buttons or knobs, but via switches.

Saw Core
A kind of oscillator, that generates a saw wave and it derives the other waveforms from that core-waveform.


A kind of oscillator, that generates a triangle wave and it derives the other waveforms from that core-waveform.

A special control signal. Any rectangular waveform can be used as a trigger signal to change logical functions or start musical events.

Unipolar voltage. E.g. a module's in- or output only sends negative or positive voltages.

A vactrol is a circuit based on a light depending resistor. Vactrol-based modules usually have a smoother response, so their sound is usually described as soft or mellow.  

Voltage controlled amplifier. Special VCAs can process both audio and CV signals.

Voltage Controlled Filter. It only sends a limited range of the input audio signal's harmonics to its output. This range depends on the filter's category.  

Vltage Controlled Oscillator. The analog oscillators usually generate a clean (subtractive) waveform within a circuit. Digital oscillators usually apply various looped cyclical waveforms that are recalled from the digital memory of the module. This latter technique is called wavetable synthesis.
The waveshaper is a sound processing tool or an effect. The waveshaper is based on a mathematical function that transforms / distorts the input signal. Typically, it is applied as a standard distortion effect.

The wavefolder is a sound processing tool or an effect. More harmonic content is added to a cleaner waveform as if the original waveform was "folded" by the effect.