Any discussion about music and sound reproduction will eventually make reference to how it is presented to the listener. Of course, it all began with monophonic, but over the years technology has provided more and more choices starting with stereophonic, followed by a host of multi-phonic formats like quadraphonic, Dolby 5.1 and 6.1. Monophonic (mono) has just one prerecorded channel. Stereophonic sound (stereo) has two distinct channels, left and right.