Full context:   Mirrored mono sound is the opposite of merged stereo, since it can be a case where media with mono sound that stereo playback devices automatically mirror it with are played on both channels of the receiver. It can also mean having a mono input mixed down to stereo amplification circuitry, or a mono system with a headphone output compatible with stereo headphones. An example of an application where both merged stereo and mirror mono apply is when a compact audio cassette respectively plays back "summed" stereo channels on a mono reading head, and when a compact cassette recorded with mono sound is played back with a stereo tape head.