(1) (noun) The composite blend of live sounds and/or recorded virtual tracks to a new program, usually of fewer tracks and often to a different recording/storage medium.

(2) (verb) To produce the new composite program, adding the live sounds, recorded virtual tracks, effects and other processing such as equalizationcompressionreverb, etc., ready for the production of a recording of the desired number of tracks and on the desired recording and/or storage medium, possibly for use as a master.