Music Glossary - A

A&R
A&R is a term used in the music industry (short for Artist and Repertoire) that refers to the department of a record label responsible for scouting out new bands and artists, and then developing their talent. The A&R department links the recording artist and the record label. A&R departments often find songwriters and record producers for signed bands, schedule recording sessions and handle any necessary contractural negotiations.
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Absorption
1. The damping of a sound wave when it passes through a medium or hits a surface.

2. The ability of a material or object to absorb sound energy.

Absorption Coefficient
A number determined from the amount of sound energy absorbed from an incoming sound wave, at a specified frequency, when it encounters a material or surface under known conditions.

AC (Alternating Current)
A phased electric current that alternates the direction of current flow.

Acapella
Unaccompanied vocal performance with one or more vocalists. Letrally "In the church style".

Accelerando
An indication in Music notation to gradually increase the tempo. Often abbreviated to "accel"

Accent
The rythym of a piece of music is clarified by the use of accents. Accent signs in music notation indicate where to emppasise notes, and how they should be emphasised.

Accidental
This an all encompassing term for prefixing a Natural, Double Flat, Flat, Sharp, or Double Sharp to a note. The accidental is primarily used to indicate playing a note outwith the current key. The effect of the use of an accidental applies to all subsequent notes of the same pitch within the same bar, unless overridden by the use of another accidental.

Accodrion
Also called piano-accordian. Invented by Friedrich Buschmann of Berlin in 1822, the accordion is a portable reed organ. Metal reeds are used to produce sound using air supplied by the "squeeze box" (a hand operated bellows).

There are two basic types of accordion.

1. Two sets of press buttons that play either individual notes or chords.

2. 1 set of press buttons, and a small piano keyboard.

Acetate
Another name for a Lacquer disc

Acoustics
1. The science behind sound.

2. The features of a room or hall that shape the sound heard by a listener.

Active
A term used to describe a circuit containing transistors, ICs (integrated circuits), tubes and other devices that require power, and are able to amplify.

Active Sensing
Used by some MIDI devices to confirm that a MIDI device is connected and working correctly. This involves the sending device transmitting regular short messages to the receiving device. If active sensing messages stop being received,the receiving device will detect the error and switch off all notes.

Adagio
A slow restful tempo.

ADC
Analogue to Digital Converter is an electric circuit that converts an analogue signal into a digital representation of that signal. The ADC will sample the analogue signal at a defined sample rate. Each sample is a binary number that represents the amplitude of the sampled signal. The number of bits used to represent each sample dictate the sample resolution.

Additive Synthesis
Generation of waveforms by the combination of basic waveforms or samples.

Each constituent partial in a sound is represented by an oscillator of appropriate amplitude and frequency. The resulting outputs are then summed in order to achieve the finished sound.

ADSR
Simple envelope generator with Attack, Sustain, Decay and Release parameters.

ADT
Automatic Double Tracking is the duplication of an audio track which is delayed by a few milliseconds to emphasise the sound or give the impression of more performers.

After Fade Listen (AFL)
Facility that allows a Recording Engineer to monitor one of the channels on a Mixing Desk, at a point in the signal chain after the fader, independently of the main mix.

Aftertouch
Generation of a control signal based on the pressure applied to the keys of a MIDI keyboard. Most instruments do not implement independent pressure sensing for all keys, but instead detect the overall pressure using a common sensing strip running beneath the keys.

Aftertouch can be used to control parameters like vibrato depth or speed, filter thresholds, and more...

Aliasing
When sampling an analogue signal, the sampling frequency must be at least twice that of the highest frequency component of the analogue signal (Niquist Frequency). If not, the sampling process is inaccurate because there are insufficient points to describe each cycle of the waveform. This results in the addition of enharmonic frequencies to the audible signal.

Alignment
Process of setting up amplifier presets and positioning tape heads for optimum tape performance.

Allegro
Indication in Music notation to play quickly, and lively

Alternate Tuning
An Alternate tuning does not form a major chord when all strings are played open, although the open strings may form a chord.

Alternating Current (AC)
Alternating Current is an electricity supply that periodically reverses its direction of current flow. Mains electricity is an example of an AC electricity supply.

Alto
Highest adult male voice, also known as "Counter-tenor". Range is 2 octaves from D below middle C to D an octave above.

Ambience
The characteristic background noise and reverberation that is particular to a location.

Ampere (Amp)
The Ampere is the unit of measurement used for electric current.

Amplifier
An amplifier is a device or system that changes the amplitude of a signal. The ratio of the amplified signal to the original source signal is commonly referred to as Gain. There are acoustic amplifiers, such as the body of an acoustic guitar or a loudhailer, and electronic amplifiers. In electronics the term amplifier is used to describe the characteristic behaviour of a specific electronic component type, such as a valve, a transistor or an operational amplifier (Op-amp), or specific circuits such as a Pre-amplifier or a Power Amplifier. In more common usage the term 'amplifier' refers to a dedicated piece of electronic equipment that allows the user to control the output volume of an audio signal.

Amplitude
In simple terms, this is the peak voltage, or representation of that voltage, of an electrical signal.

Amplitude Distortion
This is a non-linear gain variation as the signal level changes.

Amplitude Modulation (AM)
Amplitude Modulation is a type of modulation where the amplitude of the carrier wave is controlled.

There are two AM techniques: Classical Amplitude Modulation and Ring Amplitude Modulation (RM).

Classical AM adds the output of one oscillator to the amplitude input of a second oscillator. The amplitude of the first oscillator is determined by the addition of a modulation index to it's amplitude input. In other words, provided the modulation index is not zero, the first oscillator modulates the amplitude of the second oscillator proportionally to the modulation index.

Ring AM applies the modulation directly to the amplitude of the second oscillator, without being added to an unmodulated carrier. If there is no modulation, there is no sound.

Analog Audio (Analogue Audio)
An Analog audio signal is a signal that represents audio as a continuously changing voltage.

Changes in the analog audio signal ultimately dictate the behaviour of the speaker. A negative change in the voltage moves the speaker cone in one direction, while a positive change in voltage moves the speaker cone in the opposite direction.

The frequency of the audio signal corresponds directly with the frequency of voltage change in the analog signal. In plain terms it is a measure of how often the signal change repeats each second. This is reasonably easy to see if the signal only contains one frequency at any one time.

For Example:

Take a low frequency sine wave signal of 50Hz (Hertz) at a fixed volume with no d.c. offset. The audio signal, and therefor the speaker, will move back and forward between (oscillate) the positive and negative voltages that represent that volume 50 times every second. As you increase the frequency to 500Hz the signal and speaker will oscillate between the signal voltages 500 times every second.

The volume of the audio signal corresponds directly with the amplitude of the signal voltage. More accurately it corresponds with the change in voltage. This is also easy to see if we use a fixed frequency signal.

For Example:

Take a low volume signal at a fixed frequency of 50Hz (Hertz) with no d.c. offset. The audio signal, and therefor the speaker, will move back and forward between (oscillate) the positive and negative voltages that represent that volume 50 times every second. As you increase the volume of the signal the total voltage change of the signal also increases, as does the total movement of the speaker cone, but the time it takes to repeat the movement will stay the same.

Analog or Analogue
This is a continuous electrical signal whose amplitude varies with time Within the audio domain the amplitude of the electrical signal will vary in a way that has a direct relationship with the volume of the original acoustic sound wave it represents.

Analog to Digital Converter (ADC)
This is an electronic device that is used to convert analog audio signals into digital audio signals, or more generally to convert analog signals into digital signals.

Anechoic Chamber
This is a room that is specially designed to produce to no echo. This is due to acoustic design using material that completely absorbs sound energy.

Anti-Aliasing
This is a type of filter used to limit the frequency range of an analogue signal prior to input to an ADC so that the Nyquist Frequency is not compromised and an accurate sample is created.

Arpeggiator
A component that allows a MIDI instrument to sequence around any notes currently being played. i.e. Arpeggio.

Arpeggio
The production of the tones of a chord in succession and not simultaneously

Arrangement
1)Harmony setting of an existing melody for voices or instruments.

2)Adaptation of a piece of music to make it suitable for a different set of performers than was originally envisioned at the time of writing.

Aspect Ratio
This is the proportion of height to width.

Atmosphere Microphone
This is a microphone that is situated some distance from the performers in order to capture the ambience of the recording location. Typically overhead.

Atonality
Strictly a description of music that rejects traditional tonality, but it is commonly used to describe music using unfamiliar harmony.

Attack Time
The attack time means slightly different things in different circumstances. When applied to compressors and limiters it is the time from when the input sound crosses the threshold until the compression begins to be applied. With effects or synthesis it is the time from when an treatment begins to be applied until the a envelop reaches its peak.

Attenuation
Attenuation is the reduction of signal strength, either intentionally or unintentionally. This can be achieved in the electronic domain by using a volume or loudness control. Attenuation can also be applied acoustically by using materials that have absorption properties.

Audio Frequency
This is the frequency range that corresponds to the frequencies audible to the human ear, from 20 Hz to 20 kHz.

Auto-locate
This is the ability provided by audio recorders to quickly get to a chosen point, known as a locate point, within a recording or recording tape.

Auxiliary Send
A Mixing Desk output made up of a mix of channel signals or group signals that is independent of the main mix outputs. Auxiliary outputs are often used for sending to effects units.

Azimuth
This is the angle between the gap in a tape head and the longitudinal axis of a tape. The angle should be 90 degrees.