Sometimes audio mixing is done live by a sound engineer, for example at rock concerts and other musical performances where a public address system 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.
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.
An audio mixing console or desk (Brit.) may have several controls such as rotating or sliding knobs, one for each channel of audio. Each channel of the console may have other knobs which equalize, or attenuate certain frequencies, of the incoming audio signal. Larger and more complex consoles such as are used in film and television production can contain dozens of channels, and they may be automated so that the movement of the console's controls is performed automatically, not unlike a player piano.