> For the complete documentation index, see [llms.txt](https://hosted-by.gitbook.io/eurorack-synthesizers-for-dummies/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hosted-by.gitbook.io/eurorack-synthesizers-for-dummies/literature-and-references/5-2-glossary-of-terms.md).

# Glossary of Terms

**Amplifier:** A circuit or device that alters the amplitude of a signal.

**AR Envelope**: An acronym for a simple two-stage modulation envelope: Attack, Release. Typically implies a Sustain stage held high as long as the gate is active.

**Attack:** The first stage of an envelope, which establishes the length of time it takes for an envelope to reach its peak voltage after the initiating key or gate is received.

**Attenuator:** A tool used to decrease the amplitude of a signal.

**Attenuverter:** A type of attenuator that can also invert the polarity of a signal.

**Audio:** In Eurorack, audio signals are also represented as electrical voltages that fluctuate to create sound when sent to a speaker.

**Audio Rate Modulation:** Modulation where the modulating signal operates within the audible frequency range, used to create complex timbres.

**Band Pass Filter (BPF):** A filter that only passes a limited range of audio frequencies, rejecting everything below and above the specified band.

**Boat:** A deeper Eurorack case.

**Buffered Multiple:** A powered signal splitter module that uses a buffer to minimize voltage droop that can occur with passive signal splitting. Also known as an Active Multiple.

**Bus Board:** Part of the power supply system within a Eurorack case that distributes power to the modules via ribbon cables.

**Carrier:** In FM synthesis, the oscillator that produces the sound we hear, whose frequency is modulated by another oscillator.

**Case:** The enclosure that houses the Eurorack modules and often contains the power supply. Also known as a Rack.

**Clock:** A component or device in a synthesizer that produces clean, precisely-timed pulses according to a set frequency, serving as a time reference for synchronizing other parts of the system.

**Clock Divider:** A module that receives a clock pulse and generates slower clock pulses at its output(s) related to musical timing conventions.

**Clock Multiplier:** A module that receives a clock pulse and generates faster clock pulses at its output(s) relevant to musical timing.

**Complex Oscillator:** A type of sound generator, inspired by Buchla instruments, typically based on two interconnected oscillators with built-in waveshaping.

**Composite Waveform:** A waveform which contains more than one waveform, such as square, sawtooth, and triangle waves.

**Compressor:** A dynamic effect that boosts the volume of a signal and then reduces the peaks beyond a certain threshold, used to control dynamics and add sustain.

**Connector:** The physical interface on a module or cable for signal transfer. Common types include 3.5mm (⅛") mono (TS) and stereo (TRS) jacks.

**Control Voltage (CV):** Signals (usually at relatively low frequencies) carried over patch cables to allow one module to influence the behavior of another module over time.

**Current Draw:** The amount of electrical current a module consumes, usually measured in milliamperes (mA).
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Cutoff Frequency: The point at which a filter begins to attenuate frequencies.

**DAW (Digital Audio Workstation):** A software application used for recording, editing, and producing audio.
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DC Coupled: An input that can accept and pass constant or slowly changing DC voltages without altering them.
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Decay: The stage of an envelope that determines the time it takes for the signal to fall from the peak to the sustain level.

**Delay (Audio Effect):** An echo-like effect where an input signal is recorded, stored, and played back later.

**Digital Synthesizer:** A synthesizer that produces sounds using digital signal processing.

**Diode Ladder Filter:** A filter design employing a "diode ladder" in its core circuitry, known for its characteristic sound, famously used in the Roland TB-303.

**Distortion:** A type of non-linear audio effect that drastically alters a sound's harmonic content and amplitude.

**DIY (Do It Yourself):** In the context of synthesizers, DIY refers to the act of building synthesizers either from a kit or from individual electronic components.

**East Coast Synthesis:** An approach to electronic instrument design, inspired by Moog's early modular synthesizers, typically involving subtractive synthesis.

**Envelope:** A (usually) unipolar modulation signal that determines the change of a given parameter of a sound over time.

**Eurorack:** A popular modular synthesizer format established by Doepfer, characterized by compact 3U and 1U module sizes, 3.5mm mono jacks, and a +/- 12V DC power bus.

**FM Synthesis:** Frequency Modulation synthesis, a technique that uses one oscillator (modulator) to modulate the frequency of another oscillator (carrier) to create complex timbres.

**Filter:** A processor that removes certain frequencies and harmonics from a sound and allows others to pass through.

**Filter Slope:** Measured in decibels per octave (dB/octave), determines the steepness of the filter's attenuation.

**Flanger:** An audio effect created by mixing a slightly delayed copy of a signal with the original, with the delay time modulated by an LFO.

**Format Converter / Format Jumbler:** A utility device used for interconnecting modular synthesizers of different formats that use different types of patch cables.

**Function Generator:** A module that can generate various types of signals, often used for creating envelopes or LFO-like modulations.

**Gate:** In analog synthesizers, a modulation signal with only two states (low and high), typically produced by keyboards and sequencers, used to start/stop musical events.

**Granular Synthesis:** A sound synthesis technique that operates on the microsound time scale, dividing audio into tiny grains for manipulation.

**Horizontal Pitch (HP):** A unit of measure for the horizontal width of Eurorack format synthesizer modules, where 1HP equals 5.08mm.

**High Pass Filter (HPF):** A filter that allows frequencies above its cutoff frequency to pass and reduces the level of lower harmonics below the cutoff.

**Impedance:** The measure of how something resists the flow of energy. Important for matching signal levels between different types of equipment.

**Inverter:** A module that multiplies an incoming control voltage by -1, often used to reverse the polarity of a signal. Also known as a Polarizer.

**Jack:** A connector socket on a module, typically 3.5mm (⅛") in Eurorack.

**Karplus Strong:** A physical modeling synthesis algorithm designed to replicate the sound of plucked, vibrating strings.

**Limiter:** A dynamic processor that prevents a signal from exceeding a set amplitude threshold.

**Line Level:** A standard audio signal level used by most consumer and lower-cost professional audio equipment.

**Linear Power Supply:** A type of power supply known for its stable voltage and reduced noise.

**Linear VCA:** A voltage-controlled amplifier with a linear relationship between control voltage and output level.

**Logic Modules:** Modules that perform Boolean logic operations (AND, OR, NOT, etc.) on gate and trigger signals.

**Low Frequency Oscillator (LFO):** An oscillator that produces an output below the range of human hearing, used to impart cyclical modulation.

**Low Pass Filter (LPF):** A filter that allows frequencies below its cutoff frequency to pass and reduces the level of higher harmonics above the cutoff.

**Low Pass Gate (LPG):** A dynamics management module that combines the qualities of a voltage-controlled amplifier and a non-resonant low-pass filter.

**mA (milliampere):** The standard unit used to measure electrical current.

**Matrix Mixer:** A special kind of signal mixer that allows routing multiple inputs to multiple outputs.

**MIDI (Musical Instrument Digital Interface):** A digital protocol used to transmit control information between electronic musical instruments and computers.

**MIDI-to-CV Converter:** A module that receives MIDI data and translates it into corresponding CV signals.

**Mixer:** A device used for combining multiple audio signals into single, dual, or multiple output signals.

**Module:** An individual component of a modular synthesizer that performs a specific function.

**Mono:** An audio signal with a single channel.

**Moog Ladder Filter:** An iconic low-pass filter design, first developed by Robert Moog.

**Mult:** Short for Multiple, a module that copies a single input signal to multiple outputs.

**Normalled:** A default internal signal connection within a semi-modular synthesizer that can be overridden by patching.

**Notch Filter:** A filter that attenuates a narrow band of frequencies. Also known as a Band Reject Filter.

**Offset:** Adding a fixed voltage to a signal, shifting its overall voltage range.

**Operator:** In FM synthesis, refers to an oscillator, which can act as either a carrier or a modulator.

**Oscillator:** A component of a synthesizer that produces periodic waveforms.

**Patch:** In modular synthesis, an arrangement of modules interconnected to create distinct sounds.

**Patch Bay:** A device with input and output sockets used to provide a central location for convenient inter-device signal routing.

**Patch Cable:** A cable used for interconnecting modules in a modular synthesizer, typically 3.5mm (⅛") mono (TS) cables in Eurorack.

**Phaser:** An audio effect created by blending the dry signal with a copy passed through a series of variable all-pass filters.

**Ping:** An input on some modules (like filters or LPGs) that, when triggered by a gate or trigger, creates a short, percussive envelope internally routed to a parameter like cutoff frequency.

**Pingable:** Describes a module with a "Ping" input.

**Pitch (1V/OCT):** The standard in Eurorack where a 1-volt increase in CV corresponds to a one-octave increase in pitch.

**Polarizer:** See Inverter.

**Polyrhythm:** The simultaneous occurrence of two or more conflicting rhythms.

**Polyphony:** The ability of a synthesizer to play multiple notes simultaneously.

**Portamento:** A glide between notes, created by causing the pitch control voltage to slide from one note to the next. Also known as Glide.

**Power Supply:** The component that provides the necessary electrical power to the modules in a Eurorack case.

**Pulse Width**: The duration of the high portion of a pulse wave or square wave's cycle.

**Quantizer**: A device or module that receives a continuous voltage signal and outputs the nearest voltage corresponding to a note in a selected musical scale.

**Rack**: See Case.

**Ramp**: A voltage that steadily rises or falls, often used to describe the shape of certain waveforms or envelope stages.

**Ratchet**: A sequencing technique that causes certain notes to repeat multiple times at a faster rate than a set clock rate.

**Release**: The final stage of an envelope, determining the time it takes for the signal to fall from the sustain level to zero after the gate is released.

**Resonance**: A boost in amplitude at or near the cutoff frequency of a filter.

**Ring Modulator**: A type of sound processor that manipulates the amplitude of a carrier signal with another signal (modulator), resulting in an output containing only sum and difference frequencies.

**Sample and Hold**: A device that captures the value of a continuous analog signal at its input and holds it at the output for a duration specified by a trigger.

**Sawtooth Wave**: A waveform characterized by a sharp rise and gradual fall, rich in harmonics.

**Sequencer**: A hardware or software controller device used to record and organize musical events across single or multiple playable timelines.

**Semi-Modular Synth**: A synthesizer with default internal signal connections that can be overridden using patch points.

**Sine Wave**: A basic analog waveform with evenly-spaced curves and a smooth tone, often referred to as the fundamental.

**Skiff**: A portable, shallow enclosure for Eurorack modular synthesizers.

**Slew Limiter**: A circuit that limits a signal's possible rate of change, often used to smooth jittery signals or create glide/portamento effects. Also known as a Slope Generator or Lag Processor.

**Square Wave**: A waveform that alternates abruptly between two voltage levels, rich in odd harmonics.

**Stereo**: An audio signal with two channels, typically left and right.

**Strike**: An input found on some modules that use vactrols, designed to create percussive sounds and attacks.

**Subtractive Synthesis**: A synthesis technique that creates sounds by filtering harmonically rich waveforms to shape their timbre.

**Sustain**: The level at which the signal is held while the gate is active in an ADSR envelope.

**Sync**: In the context of oscillators, a mode where one oscillator resets its waveform based on the cycle of another oscillator.

**Synthesis**: The process of creating sound electronically.

**Tempo**: The speed or pace of a musical piece, often measured in beats per minute (BPM).

**Through-Zero FM**: A type of frequency modulation where the carrier frequency can go below zero, resulting in cleaner and more harmonically rich FM sounds.

**Track & Hold**: A variation of Sample & Hold where the output tracks the input voltage while the gate is high and holds the last value when the gate goes low.

**Tracking**: Refers to how well an oscillator follows the pitch control voltage sent to it.

**Transistor Ladder Filter**: An iconic low-pass filter design, known for its warm, round, bassy response.

**Trigger**: A brief, instantaneous pulse of voltage used to initiate a specific action within a module.

**Triangle Wave**: A waveform with a symmetrical triangular shape, containing only odd harmonics.

**TRS (Tip-Ring-Sleeve)**: A type of connector with three conductive parts, commonly used for stereo audio or balanced mono signals.

**TS (Tip-Sleeve)**: A type of connector with two conductive parts, commonly used for mono audio or control voltage signals.

**Unit (U)**: A unit of measurement for the height of Eurorack cases, with each row typically being 3U.

**V (Voltage)**: Refers to the electromagnetic pressure of a power source.

**Vactrol**: A light-dependent resistor placed next to a light source, used in some modules to control parameters with a characteristic slow response.

**VCA (Voltage Controlled Amplifier)**: An amplifier whose level parameter can be controlled and modulated by a voltage input.

**VCF (Voltage Controlled Filter)**: A filter whose parameters, such as cutoff frequency, can be controlled and modulated by a voltage input.

**VCO (Voltage Controlled Oscillator)**: An analog oscillator whose parameters, most commonly pitch/frequency, can be controlled and modulated by a voltage input.

**Velocity**: In MIDI, the force with which a key is pressed, often translated to control parameters like volume or filter cutoff in Eurorack via MIDI-to-CV converters.

**Wavefolder**: A specific type of waveshaping that inverts the peaks of a waveform into a series of folds once its amplitude exceeds a set threshold.

**Waveform**: The shape of a periodic signal, such as sine, square, sawtooth, or triangle.

**Waveshaper**: A device or circuit that transforms one type of waveform into another.

**West Coast Synthesis**: An approach to electronic instrument design, inspired by Donald Buchla, often involving complex waveform generation and audio rate modulation.