Audio Glossary
Stereo · aka M/S, mid-side EQ
WHAT IS
MID/SIDE (M/S) PROCESSING?
Mid/side processing splits a stereo signal into a mid channel (what's common to both speakers — usually vocals, kick, bass, snare) and a side channel (what differs — usually reverb, wide synths, stereo effects). Processing them independently lets you EQ, compress, or widen the center and the sides separately for precise stereo control.
What M/S unlocks in mastering
In a normal left/right setup, every move affects the whole stereo image. M/S decouples the center from the sides. Now you can tighten the low end by keeping bass mono in the mid channel, add air to the sides without making the vocal harsh, or widen the stereo field without smearing the kick and snare that hold the center.
It's the reason a mastered track can sound both wider *and* more focused than the mix. The two most common M/S moves: high-pass the side channel below ~120 Hz for a tight, mono-compatible low end, and gently boost the sides in the high frequencies for width and air. Every chain in the Ultimate Master Chain uses M/S routing for exactly this.
Quick answers
MID/SIDE (M/S) PROCESSING FAQ.
What is mid/side processing used for?
It lets you process the center of a stereo image (vocals, kick, bass) separately from the sides (reverb, wide synths). Common uses: keeping low end mono for punch, and widening or adding air to the sides without affecting the vocal.
Should bass be mono or stereo?
Keep low frequencies (below roughly 100-120 Hz) mono. Stereo bass causes phase issues on big systems and wastes headroom. Use mid/side processing to mono the lows while keeping the rest of the track wide.
Related terms
The tool for it
Ultimate Master Chain — Ozone
The cleanest, most surgical master in the catalog. Works with Ozone 9, 10, 11 & 12.
View in the shop →