Mid-Side Processing

Mid-side processing decodes a stereo signal into two streams: the mid, which holds everything common to both channels (usually kick, bass, snare, and lead vocal down the center), and the side, which holds the differences that create stereo width. Working on them separately opens up moves ordinary stereo processing cannot make. You can EQ air into the sides for width without smearing the center, keep low frequencies mono for a tight foundation, or compress the mid to firm up the core of the mix. It is widely used in mastering and on group buses. The two streams are re-encoded back to standard left and right afterward, so the finished file stays compatible on every playback system.