Mid/Side processing is one of the most powerful techniques in mixing and mastering — it lets you process the center (Mid) and sides (Side) of a stereo track independently. Once you understand it, you'll use it on almost every mix.
The Mid signal contains everything common to both L and R: kick, bass, lead vocal, snare. The Side signal contains everything that differs between L and R: room reverb, panned guitars, wide synth pads. This concept dates back to 1933, pioneered by EMI engineer Alan Blumlein.
Pro Tip: When mastering for streaming, always high-pass the Side channel around 80–120Hz. Streaming loudness normalization can exaggerate low-end side energy and cause mono playback issues on phone speakers.
Mid/Side EQ gives you a level of stereo control that standard EQing simply can't match. Start applying it to your mix and master buses — even subtle moves make a noticeable difference in width, depth, and clarity.
