Digital Audio Final Terms

AC3 Dolby Digital

Aftertouch 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.

All notes off A three byte MIDI channel message that instructs the receiving device to terminate all notes currently sounding.

Arpeggiate To play the notes of a chord in succession rather than simultaneously.

ATR Audio tape recorder.

Attack The initial stage of an envelope. Refers to the time taken for a sound to achieve maximum amplitude. Drums have a fast attack, whereas bowed strings have a slow attack. In compressors and gates, the attack time equates to how quickly the processor can change its gain.

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.

Bank A storage location in a sampler or synthesiser that typically holds a large number of individual programs (sounds).

Bi-amplify The use of two amplifiers, one for the lows, one for the highs. Could be built into the speaker design or accomplished with the use of external amplifiers and electronic crossovers.

Bouncing The process of mixing two or more recorded tracks and re-recording these on to another track.

BPM Beats per minute.

Bulk dump A MIDI function that allow the transfer of system specific data, such as sample files or mixer settings, between MIDI capable devices. The data is transmitted as MIDI System Exclusive messages.

Channel (MIDI) Refers to one of 16 possible data channel over which MIDI data may be sent. The organisation of data by channels means that up to 16 different MIDI instruments or parts may be addressed using a single cable.

Channel (mixer) A single strip of controls in a mixing console relating to either a single input or a pair of main/monitor inputs.

Channel message A type of MIDI message that carries specific channel information.

Chord Three or more different musical notes played at the same time.

Continuous controller A type of MIDI message that is generated by the movement of a continuous control, such as from a pedal, wheel or breath control device.

Crossover An electronic circuit that divides an audio signal into high- and low-frequency components. In many computer speakers, a crossover routes high-frequency sounds to satellite modules and low frequencies to the bass unit. The split point between the two is called the crossover frequency.

Crosstalk Unwanted breakthrough of one channel into another. Also refers to the distortion that occurs when some signal from a music source that you are not listening to leaks into the circuit of the source that you are listening to.

Damping Refers to the ability of an audio component to stop after the signal ends. For example, if a drum is struck with a mallet, the sound will reach a peak level and then decay in a certain amount of time to no sound. An audio component that allows the decay to drag on too long has poor damping and less definition than it should. An audio component that is overdamped does not allow the initial energy to reach the full peak and cuts the decay short. Boomy or muddy sound is often the result of underdamped systems. Dry or lifeless sound may be the result of an overdamped system.

DAT Digital Audio Tape; an audio tape format that uses linear digital encoding to produce audio with the dynamic range and clarity of a CD on a cassette that is 30% smaller than a regular audiocassette. The commonly used DAT machines are more correctly known as R-DAT because they use a rotating head similar to a video recorder. Digital recorders using fixed or stationary heads (such as DCC) are known as S-DAT machines.

DIN plug A five-pin connector used by MIDI equipment.

Decay One of the four basic stages of an envelope. Refers to the time the sound takes to settle into its sustain level.

Delay A common effect in a sampler or synthesiser that mimics the time difference between the arrival of a direct sound and the first reflection to reach the listener's ears.

Dither Dithering is a mathematical process where a random noise is added to the least significant bit of a digital word. With very low level signals, the quantization error becomes correlated to the signal level. This creates a measurable amount of distortion. By adding dither, the correlation between the signal level and the quantization error is cancelled, allowing the digital system to encode amplitudes smaller than the least significant bit. If you change the word size as a signal passes from one digital system to another, being able to add dither allows you to maintain a high quality signal. Dither is absolutely required for good digital audio recording and processing.

Dolby noise reduction Circuitry designed and licensed by Dolby Laboratories, used to suppress noise (extraneous sound or interference) during recording and playback of audiocassettes. Dolby B and Dolby C both amplify weaker sounds during the recording process, and return them to correct levels during playback to increase dynamic range. Dolby S is the most advanced form. Used in record and playback modes, it can enhance an audiocassette deck's dynamic range to near CD quality.

Driver Piece of software that handles communications between the main program and a hardware peripheral, such as a soundcard, printer or scanner.

Drum machine An electronic device, usually controllable via MIDI commands, that contains samples of acoustic drum sounds. Used to create percussion parts and patterns.

Drum pad Synthetic playing surface which produces electronic trigger signals in response to being hit with drum sticks.

Dubbing Adding further material to an existing recording. Also known as overdubbing.

Effect Device for treating an audio signal in order to change it in some creative way. Effects often involve the use of delay circuits, and include such treatments as reverb and echo.

Electrostatic speaker A speaker that radiates sound from a large diaphragm that is suspended between high-voltage grids.

Effects return Additional mixer input designed to accommodate the output from an effects unit.

Equalizer Device for selectively cutting or boosting selected parts of the audio spectrum.

Gain To increase in level. The function of a volume control.

Gold plated plug Gold plating prevents oxidation of the plug's surface, minimising the contact resistance and transmission loss that occurs over time.

Haas effect If sounds arrive from several sources, the ears and brain will identify only the nearest. In other words, if our ears receive similar sounds coming from various sources, the brain will latch on to the sound that arrives first. If the time difference is up to 50 milliseconds, the early arrival sound can dominate the later arrival sound, even if the later arrival is as much as 10 dB louder. The discovery of this effect is attributed to Halmut Haas in 1949.

Harmonics Also called overtones, these are vibrations at frequencies that are multiples of the fundamental. Harmonics extend without limit beyond the audible range. They are characterised as even-order and odd-order harmonics. A second-order harmonic is two times the frequency of the fundamental; a third order is three times the fundamental; a fourth order is four times the fundamental; and so forth. Each even-order harmonic: second, fourth, sixth, etc. is one octave or multiples of one octave higher than the fundamental; these even-order overtones are therefore musically related to the fundamental. Odd-order harmonics, on the other hand: third, fifth, seventh, and up-create a series of notes that are not related to any octave overtones and therefore may have an unpleasant sound. Audio systems that emphasise odd-order harmonics tend to have a harsh, hard quality.

Loop To repeat a sequencer pattern or portion of an audio sample repeatedly. The point to which the program returns, whether the beginning or some other point, is usually definable by the user.

mA milliamp or one thousandth of an amp.

Metronome A device or software function that produces a discrete pulse. Used to synchronise music with a specific tempo.

MIDI Musical Instrument Digital Interface. An international standard for communication between a musical instrument and a computer.

Mixer A recording device that allows several different audio sources to be combined. Provides independent control over each signal's loudness and stereo position.

Multiplex The ability to add or remove a pre-recorded lead singer's vocal from cassette tapes, CD+G discs and other Karaoke software. If your Karaoke software contains multiplex recording such as a duet, you can then use this feature to sing either one of the vocals.

Multitimbral Having the ability to produce many different musical timbres (sounds) at once.

Multitrack A recording device capable of recording several parallel parts or tracks which may then be mixed or re-recorded independently.

Octave A frequency ratio of 2:1. A musical distance (interval) of 12 semitones. When a frequency or pitch is transposed up by one octave, its frequency is doubled.

Overdub To record one sound on top of another; to add another part to a multitrack recording or to replace one of the existing parts.

Pan To move a signal from the left to the right of a stereo field, or vice versa.

Polyphonic The ability to play many different notes at once.

Portamento A gliding effect that allows a sound to change pitch at a gradual rate, rather than abruptly.

Punch-in The action of placing an already recorded track into record at the correct time during playback, so that the existing material may be extended or replaced.

Punch-out The action of switching a tape machine (or other recording device) out of record after executing a punch-in. With most multitrack machines, both punching in and punching out can be accomplished without stopping the tape.

Quantization The encoding process when the analog input is approximated (quantized) to the nearest binary value available. In a sequencer, used to adjust recorded material so it will be performed precisely on a selected division of the beat.

Realtime A recording or realization of a sound processing procedure as it occurs (being recorded or played back). The opposite is off-line, where the signal is processed in non-realtime.

Release The time taken for a level or gain to return to normal. Often used to describe the rate at which a synthesised sound reduces in level after a key has been released.

Sequencer Software or, less commonly, a hardware device that can record, edit and playback a sequence of audio data.

Step time Entering notes one by one, as opposed to realtime recording in a sequencer.

Streaming (audio) Refers to the process of making a broadcast of audio available on the Internet. Basically, the broadcaster puts together a set of songs and plays them from their Internet server. They then make the server available to other Internet users. The increasing availability and quality of Internet access has led to a massive proliferation of such broadcasters. This is because anyone with the right pieces of software and Internet server space (which virtually anyone with Internet access can obtain for free) can administer an Internet audio stream. Most digital audio player software applications can play Internet audio streams.

Subwoofer A speaker designed to deliver extremely low-frequency sound (usually below 100 Hz). A true subwoofer should be able to at least reach into the bottom octave (20-40Hz). Active subwoofers have built-in crossover circuitry to filter the low-frequency signal.

Tempo the rate of speed at which a musical composition proceeds (i.e. the beat). Usually uses a quarter note as the timing reference.

Timbre The quality of a sound that distinguishes it from other sounds of the same pitch and volume. The distinctive tone of an instrument or a singing voice. Tone colour.

Track The term dates back to multitrack tape where the tracks are physical stripes of recorded material, located side by side along the length of the tape.

Transpose To shift a musical signal by a fixed number of semitones.

Tremelo A rapid alternation of two tones, usually a third apart.

Tweeter A speaker used to reproduce the higher range of frequencies. To form a full-range system, a tweeter needs to be combined with a woofer, (2-way system), or a woofer and midrange, (3-way system).

Unison To play the same melody using two or more different instruments or voices.

Vibrato Pitch modulation.

Woofer A speaker used for low-frequency reproduction. Usually larger and heavier than a midrange or tweeter.