(1) A system is said to be linear if it meets the conditions of proportionality and additivity: if its output level changes smoothly in proportion to input level changes, and if input x causes output X and input y causes output Y, then x + y at the input must cause X + Y at the output. Most tests in audio including frequency responsegainphaseimpulse response, etc. assume linearity.

(2) Uncompressed, i.e., an audio file that has not been processed by some kind of compression algorithm, such as ADPCM.

(3) A process which works in a sequential fashion, such as magnetic tape recording, playback the or editing tape media, etc., as opposed to a sequence of steps which can be taken in any order and/or in any location, such as the random-access editing and playback processes which are made possible by digital storage technology.