Apple Logic Express 7 - Manual (Page 141)

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Glossary
AD converter or ADC Short for analog/digital converter; a device that converts an
analog signal to a digital signal.
aftertouch MIDI data-type generated by pressure on keys after they have been struck.
There are two types: Channel aftertouch, the value of which is measured by a full
length keyboard sensor. It affects all played notes. Polyphonic aftertouch (rare) is
individually measured and transmitted for each key. Aftertouch is also known as
pressure.
AIFF Abbreviation for Audio Interchange File Format. A cross-platform file format
supported by a large number of digital video and audio editing applications. AIFF
audio can use a variety of bit depths, but the two most commonly used are 16 bit and
24 bit.
AKAI Common sample format that the EXS24 is compatible with.
alias A pointer to a MIDI Region in the Arrange window. An alias does not contain any
data. It simply points to the data of the original MIDI Region. You can create an alias by
Shift-Option-dragging the original MIDI Region to a new location. An alias can not be
edited directly. Any change to the original Region will be reflected in the alias.
aliasing A digital artefact that occurs when the sample material contains frequencies
higher than one-half of the sample rate.
allpass filter A filter that allows all frequencies to pass, providing only phase shift or
phase delay without appreciably changing the amplitude characteristic.
amplifier Device which controls the level of a signal.
amplitude This term is used to describe the amount of a signal. If you have an audio
signal, amplitude refers to the sound’s volume, measured in decibels (dB).
analog signal A description of data that consists of a constantly varying voltage level,
that represents audio information. Analog signals must be digitized, or captured, for
use in Logic. Compare with digital.