Audio mixing is used in sound recording, audio editing and sound systems to balance the relative volume and frequency content of a number of sound sources. Typically, these sound sources are the different musical instruments in a band or the sections of an orchestra.
Sometimes audio mixing is done live by a sound engineer, for example at rock concerts and other musical performances where a public address system (PA) is used. A typical concert has two mixers, one located in the audience to mix the PA heard by the audience, and the other is located at the side of the stage, mixing for the monitor speakers positioned directly in front of the performers so that they can hear one another.
Another example of live mixing is a DJ mixing two records together. Break beats are created by mixing between identical breaks. Often the end of one pre-recorded song is mixed into another so that the transition is seamless, which is done through beat-matching or beat-mixing, and possibly pitch control.
At other times, audio mixing is done in studios as part of multitrack recording in order to produce audio recordings for release on Compact Disc or as part of a film or television program. See: remix.
An audio mixing console or mixing desk (Brit.) has numerous rotating controls (potentiometers) and sliding switches (faders) that are used to manipulate the volume and frequency content (equalization) of audio signals. On most consoles, all the controls that apply to a single channel of audio are arranged in a vertical column called a channel strip. Larger and more complex consoles such as those used in film and television production can contain hundreds of channel strips. These consoles may even have automation capabilities so the movement of their controls is performed automatically, not unlike a player piano.
Audio mixing on a personal computer is also gaining momentum. More and more independent artist are starting to use their personal computers for digital recording and mixing their work. Audio editing on the computer is also easy and preferred in some cases.