Listen to these examples through a good set of stereo speakers or using headphones.

Before 5.1 or Atmos, back in the 1960s, there was only mono and stereo audio. True mono meant that there was only a single audio track that was played back through a single speaker.

• Once stereo arrived on the scene, mono was put out as the exact same signal coming from both speakers at the exact same time. As stereo started becoming the norm, many record labels set about to reprocess mono recordings to produce a quasi-stereo signal.

• ”Regular” Fake Stereo simply slashed all the treble from one stereo channel and all the bass from the other, sometimes adding a hint of reverb to the treble channel. As both channels remained in synchronisation, fake stereo folded back nicely into mono.

• Capitol Records’ Duophonic process added a time delay of a few milliseconds to the treble channel in order to create more (fake) spatial information. Sometimes the mastering engineer also added an additional layer of compression/limiting to the signal to make it seem more lively. The problem with Duophonic was (and is) that the mono signal sounds a mess, because the left and right channels aren’t in synchronisation anymore.