A frequency coloration that cuts across many instruments is more tractable in mastering than one isolated to two competing instruments

Mastering EQ is applied to the full stereo bus — it cannot treat individual instruments separately. A narrow tonal problem is only correctable in mastering when it is shared by many elements (e.g. a 2 kHz buildup present in the vocals, snare, and guitar simultaneously can be reduced with a single broad cut that benefits all). When a problem is specific to two instruments that share a frequency range but differ in the direction of the imbalance (one too dull, one too bright in the same band), mastering EQ cannot fix both without damaging the other — that requires stem recall or a remix. Understanding this constraint helps mastering engineers set realistic expectations and communicate accurately with mix engineers.

Examples

If a vocal, snare, and guitar all sound slightly nasal at 2 kHz, a mastering cut there is well-targeted. If the vocal is dull at 3 kHz and the snare is harsh at 3 kHz, no single EQ move helps both — this is a mix problem, not a mastering problem.

Assessment

A mix arrives where the kick sounds thin and the bass sounds tubby in the 80–120 Hz region. Can mastering EQ fix this? Explain why or why not, and what advice you would give the mix engineer.