Glossary

The world of electronic music and audio has a long list of acronyms and phrases that can be difficult to figure out. This glossary is a great place to check when you come across a term you don't understand on The Sonic Spot or in any other electronic music and audio related material. If you are looking for a term that doesn't appear in the glossary, please submit the new term and the definition will be added and e-mailed to you.

 
General
 

ADSR - See Envelope.

Aliasing - A type of distortion that occurs when digitally recording high frequencies with a low sample rate. A visual analogy can be found in video, when a car's wheels appear to slowly spin backwards while the car is quickly moving forward. Similarly when you try to record a frequency greater than one half of the sampling rate (Nyquist Frequency), instead of hearing a high pitch you may hear a low frequency rumble. An anti-aliasing filter can be used to remove high-frequencies before recording. However, once a sound has been recorded, aliasing distortion is impossible to remove without also removing other frequencies from the sound.

Arpeggiator - A device that sequentially plays a pattern of notes over a range of the keyboard. The speed of the arpeggiation and pattern of notes are variable depending on the tempo and specified/pressed notes.

Attack - The initial period of a typical Envelope during which a sound's attribute (such as volume) increases from 0 (silence) to it's maximum amount. The length of the attack determines how "soft" or "harsh" a sound is. For example, most drum or percussion sounds have a short amplitude attack time and thus have a sudden "harsh" start. A string sound usually has a long amplitude attack and thus has a "soft" start and eases in.

Bandpass Filter - A type of Filter used to eliminate high- and low-range frequencies around a specific frequency, resulting in more distinctive sound.

Big-Endian - Refers to the most significant byte first order in which bytes of a multi-byte value (such as a 32-bit dword value) are stored. For example a decimal value of 457,851 is represented as 0x0006FC7B in hexidecimal and would be stored in a file as: 0x00, 0x06, 0xFC, 0x7B. Many Moterola proccessors (Macintosh) use Big-Endian. The opposite byte ordering method is called Little-Endian.

Bit/Bit-Depth - Often used to describe the resolution or quality of each sample in a digital audio stream. It is the number of bits (0's and 1's) used to describe the amplitude or volume of an audio signal at a specific point in time. The higher the number, the more precisely the original or intended audio signal can be (re)produced. See Digital Audio Basics for a more detailed explination.

BPF - See Bandpass Filter.

CDDB - A huge online database of audio CD information including album, artist, song names and more. Information is added and retreived by users of CDDB enabled software, allowing the database to continually grow. Building on the original database, CDDB2 enables expanded album and track-by-track credits, genres, web-links, segments and more. You can learn more about CDDB and CDDB2 including programming information at www.cddb.com.

Chorus - An audio effect used to "expand" or "thicken" a sound by playing multiple versions of the input signal with slightly different delays and changes in pitch simulating an ensemble of the input sound.

Codec - Stands for coder/decoder. Codecs are often used by software to compress and decompress audio data. For example, most Windows computers have an ADPCM codec which many software applications use to read and write compressed audio data from ADPCM compressed WAV files. You can view the codecs installed in Windows by going to Control Panel > Multimedia > Devices Tab > Audio Compression Codecs.

DAT - Digital Audio Tape. A tape-based digital audio recording and playback system, developed by Sony, which use a sampling rate of 48 kHz (slightly higher than CDs, which use 44.1 kHz).

Decay - The period of an Envelope during which a sound's attribute (such as volume) stabilizes after the Attack has completed. When the sound attribute reaches the end of it's decay, it has reached the Sustain period.

Delay - An effect that is used to add depth or space to an audio signal by repeating the input one or more times after a brief pause of a few milliseconds to a few seconds. Delay is also often referred to as Echo.

DirectX Plugin -

DSP - Digital Signal Processing uses mathmatics to operate on a digital signal (such as a digital audio stream) to generate some type of altered output. DSP is used heavily in software and hardware effects processing. DSP chips are found on an increasing number of Sound Card to provide extra audio processing power and help relieve the computers CPU of this type of work, much like a 3D graphics accelerator would for rendering 3D graphics.

Echo - A very basic effect produced by repeating a sound with a delay long enough to be heard as a separate event. It is often just called Delay and is usually used to add more depth to an audio signal without the muddiness often introduced by Reverb.

Envelope - Used in sound synthesis to control the volume, pan, pitch or other attribute of sound over a period of time. ADSR envelopes are the most commonly used type of envelope. They are divided into several segments, Attack, Decay, Sustain and Release. The attack segment is often triggered by pressing a keyboard note. The envelope continues and holds the sustain level until the keyboard note is released, which causes the release segment to finish the envelope.

Equalizer (EQ) - A device used to cut and boost individual frequencies of an audio signal using a number of filters. The name "equalizer" comes from the original application of correcting distorted audio signals to sound closer to the original source. Graphic Equalizer and Parametric Equalizer are different types of equalizers used by audio equipment and software Plug-In.

File Format - The structure that defines how data is organized in a software file used to store information about a sample, musical score, etc. A standardized file format makes it possible for different software programs to share the same information. See the Music and Audio File Formats Guide for more details, including information about specific file formats.

Filter - A function that cuts off a specific frequency band to change a sounds brightness, thickness and other qualities. A few common filter types are Low-pass Filter, High-pass Filter and Bandpass Filter.

Flanger - An audio effect created by varying a slight delay between two identical audio signals that results in a sound similar to a jet airplane taking off or landing.

Full-Duplex - The ability to send and receive data simultaneously which, in digital audio terms, translates to being able to play and record audio at the same time. Many sequencing and multi-track recording programs use a sound card's full-duplex capabilities to allow recording to a new track while playing back previously recorded tracks for reference. Most modern sound cards are full-duplex, but many of the older ones are only able to record or play audio at different times. They are said to be "Half-Duplex".

Graphic Equalizer - A type of Equalizer (EQ) that provides control over a fixed set of frequencies. Each filter provides linear cut/boost control over a fixed frequency. The number of filters on graphic equalizers range from three (low, mid, high) to well over eleven. While graphic equalizers generally have more filters than Parametric Equalizer, they are less flexible, in that the individual filter frequencies are not adjustable.

Half-Duplex - The inability to send and receive data simultaneously which, in digital audio terms, translates to the inability to record and play audio at the same time. Many older sound cards are half-duplex. Most modern sound cards are capable of recording and playing audio simultaneously. This capability is called "Full-Duplex".

High-pass Filter - A type of Filter used to eliminate low-range frequencies resulting in a crisper sound, good for creating percussion sounds with distinctive high ranges.

HPF - See High-pass Filter.

Little-Endian - Refers to the least significant byte first order in which bytes of a multi-byte value (such as a 32-bit dword value) are stored. For example a decimal value of 457,851 is represented as 0x0006FC7B in hexidecimal and would be stored in a file as: 0x7B, 0xFC, 0x06, 0x00. Intel processors (PC) use Little-Endian. The opposite byte ordering method is called Big-Endian.

Low Frequency Oscillator - Used in sound synthesis to modulate a sound attribute such as volume at an audibly slow rate.

Low-pass Filter - A type of Filter used to eliminate high-range frequencies resulting in a rounder sound.

LPF - See Low-pass Filter.

MIDI - Musical Instrument Digital Interface provides a standardized method for MIDI devices such as synthesizers, samplers, sound cards, etc. to communicate musical events and data to each other. See the MIDI Guide for a detailed explanation.

MIDI Interface - A hardware interface that is either inserted into one of the computer's internal expansion slots or plugged into a computer (serial/parallel) port. It allows the computer to communicate with other MIDI instruments by adding one or more MIDI input and output ports.

Mixer - A hardware or software device that combines multiple audio signals into one destination signal. Mixers usually provide control over the volume and/or stereo balance of each source signal.

Modulation - The fast oscillation of one or more operators or sound waves of a synthesized sound. Commonly used in FM synthesis to add some complexity and texture to a sound. Many MIDI controllers and keyboards provide a specific wheel or slider for controlling the modulation of an instrument sound (often referred to as the mod-wheel).

Monophonic - Only one note of an instrument may be played at a time. An instrument that can play many at once is said to be Polyphonic. Monophonic instruments usually cut-off the sound of previously played note with the start of new one.

Monotimbral - Only one instrument sound (Timbre) may be played at a time. Older synthesizers were often monotimbral before sequencers where invented, which enables musicians to play multiple parts on the same instrument. A monotimbral synthesizer may be able to play multiple notes of the one instrument sound simultaneously.

Multitimbral - More than one instrument sound (Timbre) may be played at the same time. Most modern synthesisers, samplers and sound cards have this capability. A musical device that is not multitimbral is said to be Monotimbral.

Oscillator - A synthesis module used to create a cyclical waveform. These simple waveforms may then be passed through other modules (Low Frequency Oscillator, Envelopes, etc.) to add some character. See the synthesis.html for more details.

Parametric Equalizer - A type of Equalizer (EQ) that provides control over each filter's frequency and the amount of cut or boost of each filter. Typically, parametric equalizer's provide three to four filters that work in parallel, each one filtering a different frequency of the spectrum (i.e. low, mid, high). While parametric equalizers generally have fewer filters than a Graphic Equalizer, they are more flexible and provide finer control, due to the adjustability of the filtered frequencies.

Patch - Refers to an instrument sound, program or voice on a synthesizer or sampler. This term comes from the roots of hardware synthesis, where physical cables where used to connect and route signals in a matrix to create a unique sound (same concept as phone operators "patching" a call through, back in the day).

Plug-In - A "client program" that is used to expand the functionality of a "host program", such as a sequencer or digital audio editor. The host provides the plug-in with some type of input data such as digital audio samples, which is then processed to generate new output, such as effected digital audio. A plug-in is often run seamlessly from within a host program appearing to be part of the standard interface. One plug-in can be used by multiple host programs that share the same plug-in format. Two popular plug-in formats used in computer music and audio are DirectX Plugin and VST Plugin digital audio plug-ins.

Polyphonic - More than one note of an instrument sound may be played at the same time. Hardware and software synthesizers usually range from 1 to 128 notes polyphony. The number specifies exactly how many notes may be played at once before cutting-off previously played notes. An instrument that can play only one is said to be Monophonic.

Polytimbral - More than one instrument sound (Timbre) may be played at the same time. Multitimbral is the more commonly used term for this functionality.

Potentiometer (Pot) - A variable resistor (rotary or linear) used to control volume, tone, or other function of an electronic device.

Release - The final period of an Envelope during which a sound's attribute (such as volume) decreases from the Sustain level to 0 (silence). The release period is usually started upon releasing a keyboard's note. This period of the envelope defines how a sound finishes off. A long release time causes a sound's attribute to fade away slowly, while a short release time causes it to drop out quickly.

Resample - To recalculate Sample in a sound file at a different Sample Rate than the file was originally recorded. If a sample is resampled at a lower rate, sample values are removed from the sound file, decreasing its size, but also decreasing its available frequency range and possibly introducing Aliasing. Resampling to a higher sample rate, often interpolates extra sample values into the sound file. This increases the size of the sound file but may not increase the quality (depends on the algorithm used).

Reverb - An effect that simulates natural reverberations (sound reflections) that occur in different rooms and environments to create an ambience or sense of spaciousness.

RIFF - The Resource Interchange File Format is the storage structure commonly used for multimedia data on the Windows platform. It organizes data in chunks which each have a small header that describe the chunk type and size. This structure allows programs that do not recognize specific chunk types to skip over the unknown data and continue correctly processing known chunks in the file. Data chunks may contain smaller "sub-chunks" of data. In fact, all RIFF files are supposed to store all data chunks inside a master "RIFF" chunk that defines the type of resource data the file contains. WAVE and AVI files are examples of data stored in the RIFF format.

Rip - To extract or copy data from one format to another more useful format. The most common example is found in the phrase "CD Ripping" which means to copy audio tracks from an ordinary audio CD and save them to hard disk as a WAV, MP3 or other audio file, which can then be played, edited or written back to another CD.

Sample - A sound or short piece of audio stored digitally in a computer, synthesizer or Sampler. The word sample may refer to either a single moment in a digital audio stream (the smallest piece of data used to represent an audio signal at a given time) or a complete sound or digital audio stream made up of a collection of individual samples. For a more detailed explanation of samples, see Digital Audio Basics.

Sample Rate - The resolution of digital audio that determines it's sound quality. When audio is digitally recorded (digitized), it must be converted into a series of Samples which can be stored in memory or on disk. The sample rate defines how many samples are recorded per second of audio input and is measured in Hz (Hertz, cycles per second) and kHz (Kilohertz, thousand cycles per second). Click the examples below to hear the difference between a few commonly used sample rates.

Sample Rate Example
11025Hz
22050Hz
44100Hz (CD sound quality)

Sampler - A hardware device or software application that uses Samples as it's main method of generating it's audio output. Samplers often use a number of samples together to create realistic sounding reproductions of real sounds and musical instruments. For more details on this technique, see Wavetable Synthesis.

Sequencer - A hardware device, software application or module used to arrange (ie. sequence) timed events into some order. In digital audio and music, sequencers are used to record and arrange MIDI and/or audio events into patterns and musical compositions.

Signal-to-Noise Ratio - "Signal" refers to the useful or "pure" information found in a an audio stream or other medium, and "noise" to anything else. The ratio of these is usually expressed logarithmically, in decibels. Signal-to-Noise Ratio is sometimes abbreviated as SNR, s/n ratio and s:n ratio. A high SNR translates to a "cleaner" signal.

Sound Card - A hardware interface that is either built into a computer's motherboard or inserted into one of the computer's internal expansion slots. Sound cards allow the computer to play digital audio and/or musical instrument sounds. Many sound cards also provide a MIDI Interface.

Sustain - The period of an Envelope during which a sound's attribute (such as volume) holds at a constant level. The sustain period starts at the end of the Decay period and holds until the Release period is started (usually by a keyboard note release). Unlike the other periods of an envelope, the sustain period does not have a slope because it must be capable of holding indefinitely (as long as a keyboard note is pressed).

Syncopate - To shift the regular accent of a tone or beat by beginning on an unaccented beat and continuing through the next accented beat.

Timbre - The characteristics that differentiate one instrument, voice or sound from another. It can be thought of as the texture or characteristics that define a sound. Notes of the same pitch and volume may have a different timbre. In electronic music, timbre sometimes refers to a synthesizer voice or patch (see Multitimbral).

Time Variant Amplifier - Alters the volume of an audio signal over a period of time, often based on an Envelope.

Time Variant Filter - Alters the brightness, thickness and other aspects of an audio signal over a period of time using filters, often based on an Envelope.

Time Variant Pitch - Alters the pitch of an audio signal over a period of time, often based on an Envelope.

TVF - See Time Variant Filter.

VCD - A Video CD is a compact disc which stores video and audio compressed using MPEG-1 file format technology. Movies are generally compressed to around 352x240 pixels (NTSC) resulting in about 1 GB of data, which spans over two CDs. While they aren't common in the USA, VCDs are more common in other countries where many popular electronics companies sell dedicated VCD players. DVD technology surpasses the quality of VCD technology, mostly due to the increased storage capacity of DVD media.

Vocoder - An audio effect that produces "robotic" sounding results when processing vocal input. It uses an algorithm called ring modulation to produce the effect. Examples can be found in some disco and modern music, such as the Beastie Boys' "Intergalactic".

Voltage-Controlled Amplifier - An audio signal amplifier whose output is controlled by voltage (instead of a Potentiometer (Pot)). VCAs can be used to alter the amplitude of a signal output from a Voltage-Controlled Oscillator.

Voltage-Controlled Filter - A filter whose cutoff frequency and resonant frequency is adjusted using a control voltage. VCFs are used to filter the audio signals generated by VCOs in an analog synthesizer in order to create more interesting and textured sounds.

Voltage-Controlled Oscillator - An analog circuit that generates a electrical waveform, such as a Sine, Saw or Square wave where the pitch is determined by a control voltage. VCOs are used by older analog synthesizers to generate the base sounds which are then altered by Voltage-Controlled Amplifiers and Voltage-Controlled Filters.

VST Plugin - A program that uses Steinberg's VST technology to obtain digital audio samples which are then manipulated by applying reverb, compression or some other type of audio signal effect. The output signal may be rendered off-line or generated in real-time while the plug-in's host program performs playback. See Plug-In for more details.

WMDM - Windows Media Device Manager is a Microsoft software component that enables Windows applications to share and transfer files to and from non-PC devices, such as portable MP3 players, in a standardized way. The use of a common software component enables greater software and hardware compatibility and support.