Why does my mix sound muddy? The 300 Hz fix

A muddy mix has too much going on in the low mids, roughly 200 to 500 Hz. Keys, pads, guitars, vocals and bass all have energy there, and when they pile up the mix turns thick and unclear. A wide EQ cut of 2 to 4 dB around 300 Hz on the instruments that don't need it clears the mud.

How to do it

1. Put an EQ on a pad, keys or guitar track and boost a narrow band by 8 to 10 dB.
2. Sweep it slowly between 200 and 500 Hz. Where it sounds boxy or boomy, that's the mud.
3. Turn the boost into a wide cut of 2 to 4 dB at that spot.
4. Repeat on the other tracks that crowd the low mids. Leave the bass and kick for last.
5. Listen to the whole mix again. Everything should sound clearer, not thinner.

Why it works

Every sound has its loudest energy somewhere between low and high. The low mids are where most instruments overlap, so that's where a mix fills up first. Cutting a little from many tracks works better than cutting a lot from one.