Mixing usually means combining multiple audio channels with a
fader or potentiometer for each channel that lets you determine
the channel's sound level in the overall result. In the simplest
form, each input channel is a mono channel and the output is
single channel too. You can think of each input as a pipe with a
valve, and the output as a drain beneath the valves that
collects all the water. Many sound sources are typically fed to
the mixer as mono sources--vocals, guitars, bass, individually
miked drums on a drum kit. Other sound sources are typically
recorded in stereo, such as a pair of drum kit overhead
microphones, a synthesizer that delivers stereo output, samples
of existing recordings, etc. So a typical mixer will usually
support both mono input channels and stereo input channels. In
both cases, each channel will usually feature a pan pot
(panoramic potentiometer) in addition to the fader that lets you
determine how much of the input that is sent to the left or
right channel. This can either be use