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.(as opposed to reverberation, which is a continuous wash of closely spaced, non-discrete echoing sound).
> delay (3), >reverb.

edit buffer
An area of memory used for making changes in the current patch. Usually the contents of the edit buffer will be lost when the instrument is switched off; a write operation is required to move the data to a more permanent area of memory for long-term storage.

editor/librarian
A piece of computer software that allows the user to load and store patches and banks of patches (the librarian) and edit parameters (the editor).

Effects
Any form of audio signal processing -- reverb, delay, chorusing, etc.

E-IDE
Short for "Enhanced IDE"; which is exactly what it is.

EISA
Short for "Extended ISA"; the ISA bus's big brother with 32 data circuits.

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.

envelope generator
A device that generates an envelope. Also known as a contour generator or transient generator, because the envelope is a contour (shape) that is used to create some of the transient (changing) characteristics of the sound. See ADSR, envelope.

envelope tracking
A function (also called keyboard tracking, key follow, and keyboard rate scaling) that changes the length of one or more envelope segments depending on which key on the keyboard is being played. Envelope tracking is most often used to give the higher notes shorter envelopes and the lower notes longer envelopes, mimicking the response characteristics of percussion-activated acoustic instruments, such as guitar and marimba.

event editing:
An operation in a sequencer in which one musical event at a time is altered.

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 and Parametric are different types of equalizers used by audio equipment and software plug-ins.

Encoding
The process of transforming audio into a compressed format, such as from WAV to MP3.

EPAC (Enhanced Perceptual Audio Coder)
An audio encoding method developed by Lucent Technologies.