When multiple tracks are compiled to create a stereo or surround sound file, it is known as summing. Summing will generally be performed during mix-down stages before the audio file is sent to another audio medium for additional processing (such as tape) or before compiled for regular types of mastering. The use of analog summing can prevent summing errors, which may result in sonic imperfections and glitches in audio.
Summing is a vital part of compiling multiple tracks into fewer channels (usually a stereo file or multiple surround sound) so that additional processing can be performed, such as mastering and stem mixing, and so various instruments can be easily re-introduced to a mix at a later point. If the summing is completed incorrectly or through devices limited computer or circuitry power, it can create summing errors which can cause sonic errors.
Summing can be performed through the use of in-the-box (ITB) Digital Audio Workstations (DAWs) or through outboard hardware, although hardware is proven to assist in preventing summing errors and provising high quality results. Any mixer or console can be used for summing, and mini-mixers and summing boxes have also been created to perform this without need for a full console, with some also able to pair with DAWs.