The origins of sidechain compression go back to the the 'ducking' technique. Ducking means the reduction of the volume of an audio signal by another audio signal, e.g. music is reduced by a voice. In pop music, sidechain compression has become one of the most used and most complex studio techniques to expose certain sounds like bass drums or synth hooks.
This BP spot from 1992 shows typical problems of overlapping, music, noise and speech.
This ABBA interview shows a typical ducking technique: ABBA, being interviewed by the german former Radio-journalist Thomas Gottschalk 1982 are 'ducked' in the background by Gottschalks voice.
sidechaining in Logic X
Daft Punk "One More Time" (2000). One of the first examples where sidechaining is applied on drums and synths.
David Guetta "Sexy bitch" (2010). Pumping effect on kick and bass.
Katy Perry "Teenage Dream" (2010). Pumping effect on drums and synths.
Pitbull feat. T-Pain "Hey Baby" (2011). Ducking of bass and synths, several bassdrums (some distrorted) are spread in stereo panorama.
Maroon 5 "Moves Like Jagger" (2011). Ducking of bass with an exposed kick sound
David Guetta "Titanium" (2012). Extreme pumping effect on bass and synths.
Katy Perry "Firework" (2012). Extreme pumping effect on bass and synths. Stacked kick sounds.
Katy Perry "Part Of Me" (2012). Extreme compression and complex sidechaining.
Pitbull feat. Christina Aguilera "Feel This Moment" (2013). Ducking of melody and bass.
Pitbull feat. Kesha "Timber" (2014). Ducking of bass and acoustic guitar.
To understand and recognize Sidechain Compression, here are some simple examples by the author:
Example 1 shows a bassline and kick without sidechaining
Example 2 shows a bassline and kick with sidechaining
Example 3: strings without sidechaining
Example 4: strings with sidechaining
Example 5: strings, bass and kick with sidechaining
Quick explanation of a complex system by David Guetta
One of many tutorials explaining Sidechain Compression