After setting up all the sound equipment and plugging in the musicians, mixing comes into play. Mixing is done with a large control panel called a mixing board or simply a mixer. The mixing board allows the audio engineer to mix the various sounds — guitars, bass, drums, vocal, et cetera — so that they’re in balance. All instruments, vocals and other sounds can be controlled at this central location, which audio engineers usually set up in front and away from the stage.
From that vantage point, the live concert engineer can hear what audience members hear.
Mixing boards come in many sizes, based on the number of tracks or “channels” they have. They range anywhere from eight to 124 or more channels in capacity. Each channel can accommodate an instrument or voice. Each channel also has several variables – again, depending on the board’s size and capacity. Such variables can include volume, bass, treble, effects and others.