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16 bit sound: Audio sampled using a 65,536 increment scale. When the playback material is recorded at a high sample rate (44.1Khz), the sound produced is indistinguishable from that of an audio CD.

8 bit sound: Audio based on a sample of a sound wave using 256 increments. Inferior in quality to 16 bit sound.

A Cappella: - Music which consists only of voice or voices, and is bereft of any instrumental accompaniment.

A high pass filter utilizes capacitors, as the impedance of a capacitor decreases for HIGH frequencies, this enables it to ensure the passage of higher frequencies, and stop the passage of more powerful, lower frequency signals which may blow the poor little tweeter unit to smithereens!

A Word Clock is an essential part of any digital recording system, measuring digital time in terms of digital audio "word" which is a "sample" . In "home" digital recording setups, the word clock is often an embedded part of the digital DataStream (the "S/PDIF" and "AES/EBU" interface standards are an example of this). However this can make the digital audio stream prone to "Jitter" (see above). More expensive professional systems however, tend to use a discrete word clocking system, utilizing the "BNC" standard connection. Here the time clock utilizes a square wave signal, which runs at the same sampling rate as the main audio signal.

A.D.S.R.: - Attack, Decay, Sustain, Release. See also "synthesiser"/"envelope generator"

A/D Analog to Digital Conversion: An electronic device that converts analog signals from a microphone or line level source into digital signals (digitizing or sampling them) so they can be stored to any number of storage media like hard drives, ADAT, computer ROM chip, or processed in a sampler, digital signal processor or digital recording device.

A/D Conversion / Converter: - Analogue to Digital conversion. A converter is a piece of circuitry which achieves this. The quality of conversion is highly dependent on the amount of bits used in the conversion process, hence a 24 bit converter will achieve a much more accurate resolution of the sound than say, an 8 bit converter. Circuit for converting analogue waveforms into a series of equally spaced numerical values represented by binary numbers. The more 'bits' a converter has, the greater the resolution of the sampling process.

AAC (.aac) - "Advanced Audio Coding", next generation audio codec developed by Fraunhofer that seeks to preserve audio quality at lower bitrates. High licensing costs have kept this audio codec from the mainstream

AC:- Acronym for Alternating Current, which is electrical current where electrical charge will travel in one direction, then change into moving in the opposite direction. When looked at through an oscilloscope, it's waveform is generally of a sinusoidal, square or sawtooth shape. Almost all domestic electricity found in homes is AC, with a frequency of 60 Hertz, Although virtually all electronic devices require DC power (batteries are DC) this is rectified through the use of transformers and rectifiers in the devices power supply. The reason why AC has been chosen as the standard for mains electricity when DC may be more suitable is due to it's ability to be transferred over great distances. See also DC and Rectifier.

Acoustics: - The study of sound and its behavior within an environment.

Active Crossover: - One is to split the frequencies into different bands (bass, mid, treble etc) before the signal is amplified. This is known as an "Active" kind of crossover network. This "Active" way of splitting the frequency bands is usually used where multiple power amplifiers (e.g. one amp for bass, one for mid and so on) as well as multiple drive units are used. An example of this would be a large sound re-enforcement or "PA" system of the kind seen at large rock concerts etc, whose power output may be many thousands of watts.

ACTIVE SENSING - a method by which a MIDI device detects disconnection. A message is sent to the receiver around three times per second, and if no message is received during this period, the unit assumes the MIDI connection has been broken. It then begins a routine to reestablish normal operation. A system used to verify that a MIDI connection is working, that involves the sending device sending frequent short messages to the receiving device to reassure it that all is well. If these active sensing messages stop for any reason, the receiving device will recognise a fault condition and switch off all notes. Not all MIDI devices support active sensing.

ACTIVE: Describes a circuit containing transistors, ICs, tubes and other devices, that require power to operate and are capable of amplification.

ADAT Lightpipe: A digital interface that allows 8 individual tracks to pass through an optical (Toslink) cable. Lightpipe is used with ADAT machines and is incorporated in numerous soundcards and multiple AD/DA converters. Sonorous STUDI/O is a ADAT Lightpipe soundcard.

ADAT: A trademark of Alesis Corporation for its modular digital multitrack recording system released in early 1993 and stands for Alesis Digital Audio Tape. It records eight tracks digitally on a standard 1/2" SVHS video cassette and is currently a 20-bit digital format. The ADAT optical connections for transferring the digital data 8-tracks at a time are used in a wide range of products from many manufacturers.

Additive Synthesis: A method of synthesis that builds complex waveforms by combining sine waves with independently variable frequencies and amplitudes. Envelope shapers and filters can further process these waveforms. Hammond organs and similar instruments make the most use of simple additive synthesis.

ADSR - Attack, Decay, Sustain and Release are the four stages of an envelope that describe the shape of a sound over time. Attack represents the time the sound takes to rise from an initial value of zero to its maximum level. Decay is the time for the initial falling off to the sustain level. Sustain is the time during which it remains at this level. Release is the time it takes to move from the sustain to its final level. Release typically begins when a note is let up. In most sound generators, the time and the value reached are programmable. The Attack, Decay, and Release parameters are rate or time controls. Sustain is a level. When a key is pressed, the envelope generator will begin to rise to its full level at the rate set by the attack parameter, upon reaching peak level it will begin to fall at the rate set by the decay parameter to the level set by the sustain control. The envelope will remain at the sustain level as long as the key is held down. When a key is released, it will return to zero at the rate set by the release parameter.

AES: - Acronym of the Audio Engineering Society.

AFL: After Fade listen; a system used within mixing consoles to allow specific signals to be monitored at the level set by their fader of level control knob. Aux sends are generally monitored AFL rather than PFL (see PFL).

AFTER TOUCH - a measurement of the force applied by a performer to the key on a controller after it has been depressed. Either polyphonic, which measures the pressure on each individual key, or monophonic, reflecting the total pressure on all keys. After Touch: - facility of some keyboards which allows the sonic quality of a note to be altered by further pressure after the key has been initially depressed. A means of generating a control signal based on how much pressure is applied to the keys of a MIDI keyboard. Most instruments that support this do not have independent pressure sensing for all keys, but rather detect the overall pressure by means of a sensing strip running beneath the keys. Aftertouch may be used to control such functions as vibrato depth, filter brightness, loudness and so on.

AIFF: AIFF stands for Audio Interchange File Format and was developed by Apple for storage of sounds in the data fork. The Macintosh OS includes support for playing and creating AIFF files. In addition, the format specification can be found at various places on the Internet. AIFF is a very flexible file format, allowing the specification of arbitrary sampling rates, sample size, number of channels, and application-specific format chunks which can be ignored by other applications.

ALGORITHM: A computer program designed to perform a specific task. In the context of effects units,
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.

ALIASING (FOLD-OVER) - ``false frequencies'' that are created when sampling frequencies greater than one-half the sampling rate. Unwanted frequencies produced when harmonic components in the audio signal being sampled by a digital recording device or generated within a digital sound source are above the Nyquist frequency. Aliasing is also sometimes referred to as fold-over. See Nyquist Frequency. When an analogue signal is sampled for conversion into a digital data stream, the sampling frequency must be at least twice that of the highest frequency component of the input signal. If this rule is disobeyed, the sampling process becomes ambiguous as there are insufficient points to define each cycle of the waveform, resulting in enharmonic frequencies being added to the audible signal.

Alignment Tape: - Tape using several specific tones, used for the optimisation of azimuth alignment (see below) on tape machines.

Alignment: - see "azimuth alignment".

ALL NOTES OFF - a three byte MIDI channel message that instructs the receiving device to terminate all notes currently sounding.

Altivec: A programming tool developed by Motorola, Alivec is a short vector architecture technology that accelerates software. (See vector architecture). BIAS's latest version of Peak implements an altivec-based convolution technology which allows natural reverb impulses to be applied to dry audio signals, giving the impression that a file was actually recorded in a particular environment.

AMBIENCE: In audio / acoustic terminology, this is the reverberant quality of a room . The result of sound reflections in a confined space being added to the original sound. Ambience may also be created electronically by some digital reverb units. The main difference between ambience and reverberation is that ambience doesn't have the characteristic long delay time of reverberation - the reflections mainly give the sound a sense of space.

AMP: (Ampere) Unit of electrical current. see Current

AMPLIFIER - a device that increases the amplitude, power or current of a signal. The resulting signal is a reproduction of the input signal as well as this increase.

AMPLITUDE - the strength or magnitude of any changing quantity when compared to its \Qat rest' or \Qzero' value.

Amplitude Modulation: A change in the level of a signal. For example, if a Voltage Controlled Amplifier (VCA) were being modulated by a Low Frequency Oscillator (LFO), the result would be a periodic increase and decrease in the audio level of the signal. In musical terms this would be referred to as Tremolo. The abbreviation of Amplitude Modulation is AM.

Amplitude: A digital audio file’s sound levels or electrical signal levels. It refers to the height of a waveform—the greater a sound wave's amplitude, the louder it sounds. Most software audio programs allow viewing the amplitude of the waveform for detailed editing.

ANALOG - Analog: An analog audio signal is represented by variations such as voltage speed or frequency and the strength of amplitude or volume of an electrical audio signal. The audio outputs from a computer’s soundcard or synthesizer are typically analog outputs even though the file being played is digital through a D/A converter. See D/A..

Analog Synthesis: Electronic synthesis, electronic oscillators, filters, and envelopes are used to directly create and manipulate sound. It does not involve sampling rate, bit depth, or other digital factors. (Such as older Analog Synthesizers/Keyboards used in the 1970s). A synthesizer which uses voltage controlled analog modules to synthesize sound. The three main voltage controlled modules in an analog synthesizer are: Voltage Controlled Oscillator (VCO), Voltage Controlled Filter (VCF), and Voltage Controlled Amplifier (VCA).

Anechoic / Anechoic Chamber: - Anechoic means an absence of echo / reverberation. An Anechoic chamber is a room that has been acoustically designed to have no echo. Quite a hard thing to do, it is realised by the use of materials that will completely absorb sound waves, and is important for the testing of loudspeakers etc. Said of an acoustic which is free field (i. e. without boundary or reflecting surfaces), and specifically of a room which is designed to produce no reverb or other echo effects. This is achieved by making the walls with very irregular surfaces of considerable and varying depths, in such a manner as to ensure that (in theory) all sound pressure waves which strike the walls are completely absorbed. Rooms of this type are used to test audio equipment such as loudspeakers and microphones and for other types of research.

ANTI-ALIASING FILTER: Filter used to limit the frequency range of an analogue signal prior to A/D conversion so that the maximum frequency does not exceed half the sampling rate.

Aperiodic Waveform: A waveform that does not have a repeating pattern.

APPLICATION: Alternative term for computer program.

ARP: American Recording & Performance Co, a company which introduced some amazung synthesizers in the late seventires and early eighties.

ARPEGGIATE - to play the notes of a chord in succession rather than simultaneously. 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. Device (or software), that allows a MIDI instrument to sequence around any notes currently being played. Most arpeggiators also allows the sound to be sequenced over several octaves, so that holding down a simple chord can result in an impressive repeating sequence of notes.

ASCII: American Standard Code for Information Interchange. A standard code for representing computer keyboard characters by binary data.

Asia-Pacific Economic Cooperation (APEC): Asia-Pacific Economic Cooperation, consisting of a group of countries that borders the Atlantic or Pacific Ocean, was organized to liberalize trade.

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. The initial stage of an envelope. Refers to the time from the beginning of the sound to its highest or maximum level.

Attack Time (1) The time taken for a musical or other sound to reach maximum loudness or timbre from silence. The start of a sound. (2) Of a compressor or limiter etc. The time the device takes to respond to a transition in the signal level beyond the threshold. (3) Of an envelope generator the time taken for the envelope to reach its maximum level from its off or zero position. If the EG is being used to control an amplifier (VCA or DCA) the time taken to reach maximum loudness from silence.

Attenuation A reduction in the the amount of some quality such as signal level. The property exhibited by attenuators. The opposite of amplification.

Audio Frequency The range of frequencies which can be experienced by an average human being. The range is defined as 20 Hz to 20 kHz for convenience but in practice, is realistically closer to 20 Hz to 17 kHz. Dolphins are believed to hear up to 70 kHz.

AUDIO FREQUENCY: Signals in the human audio range: nominally 20Hz to 20kHz.

Audio Home Recording Act: This 1992 legislation exempts consumers from lawsuits for copyright violations when they record music for private, noncommercial use and eases access to advanced digital audio recording technologies. The law also provides for the payment of modest royalties to music creators and copyright owners, and mandates the inclusion of the Serial Copying Management Systems in all consumer digital audio recorders to limit multi-generational audio copying (i.e., making copies of copies). This legislation will also apply to all future digital recording technologies, so Congress will not be forced to revisit the issue as each new product becomes available.

Audiophile: A person enthusiastic about sound reproduction who is discerning about the quality of the audio.

Audit: Conducted by an independent accounting firm, an audit verifies shipment and sales levels for each audio and music video format after returns. In addition, the audit calculates what product has been shipped for sale, net after returns, versus product used for promotional purposes. A formal certification report is issued and sent to the record company.

Auto Accompaniment: This generally refers to software such as PG Music’s Band in a Box that provides a ready-made back-up band.

Auto Correlation: A process that determines optimum start and ending loop points to produce minimum discontinuity.

Autolocator: - Feature of some tape machines which enable a specific location on a tape to be stored, so that later, the tape machine may locate the same cue point.

AUTOLOCATOR: Feature of a tape machine or other recording device that enables specific locations to be stored, then at some later time, these locations within the recording may be recalled. For example, you may store the start of a verse as a locate point so that you can get the tape machine to wind back the start of the verse after you've recorded an overdub.

AUX RETURN: Mixer inputs used to add effects to the mix.

AUX SEND: Physical output from a mixer Aux Send buss.

AUX: An “auxiliary” physical control knob on a mixing console designed to route a portion of the channel or channels signal to the effects or other mix outputs. Edirol’s new audio mixer, the M-100FX has aux bus ports with a stereo return and a mono send.

Auxilary Controllers: These are external controlling devices used in conjunction with a main instrument or controller. Some examples of such controllers are foot pedals, pitch bending and modulation wheels.

Azimuth (alignment): - Degree of alignment between tape head and tape. Perfect azimuth alignment is when the tape head and the tape are both are making a perfect 100% contact with each other. When this is the case, alignment is said to be at it's "zenith", and it is exactly 90 degrees between the tape-head gap, and the longitudinal axis of the tape. Good azimuth alignment is vital to the sound quality produced by any kind of tape machine, with poor quality alignment, a tape machine will often sound muffled, and somewhat lacking in "top end". Poor azimuth alignment is largely responsible for the inferior sound quality produced by many cassette recorders.