Fixing common mix problems: muddy lows and harsh vocals

Two complaints come up in almost every home mix: the low end sounds like a wet blanket, and the vocal stings on every "s" and every loud note. Both are common mix problems with well-known fixes, and the fix is usually smaller than people expect. Quite often it starts before you open a single plugin.

Check the arrangement before you reach for EQ

A muddy mix is often a crowded arrangement. Kick, bass, a low synth pad, the left hand of the piano and the low strings of a guitar all want the same space. EQ can carve some room, but it cannot fit five instruments where two belong.

Try the mute test. Loop the chorus and mute the parts one at a time. If the mix gets clearer when something disappears and you don't miss it, that part either goes, moves up an octave or plays less. A pad an octave higher often does the same emotional job without fighting the bass.

Then decide who owns the very bottom: the kick or the bass. In most styles one of them sits lower and the other just above it. Tessa Lane spent an evening EQing a ballad where piano, bass and a cello line all lived in the same register. Moving the cello up and simplifying the piano's left hand fixed more than any plugin had.

Cleaning up muddy lows

Once the arrangement makes sense, a few moves do most of the work:

• High-pass what doesn't need lows. Vocals, guitars, hi-hats, pads and effects rarely need the deepest frequencies. Sweep the filter up until the sound starts to thin out, then back off a little. There is no magic number; every source is different.
• Watch the low mids. The area roughly between 200 and 500 Hz is where mud usually builds, because so many instruments have energy there. A small cut on several tracks tends to sound more natural than a deep cut on one.
• Find the boom by ear. Make a narrow boost, sweep it slowly, and stop where the sound turns boomy or boxy. Cut that spot moderately. Then remove the boost you used for searching, and don't cut everything you hear while sweeping.
• Filter your reverbs. A long reverb with full low end turns a clean mix cloudy. Trim the lows of the reverb return, and keep bass-heavy instruments mostly dry.
• Give kick and bass separate moments. Gentle ducking of the bass when the kick hits, or complementary EQ on the two, keeps them from smearing into one note.

Finally, check on more than one system. An untreated room can hide bass or exaggerate it. Listen quietly, on headphones, on a phone speaker and in mono, and compare with a reference track you know well.

Where harsh vocals come from

Harshness is often recorded in. A singer very close to a bright condenser microphone, pushing the loud notes in a small untreated room, will sound sharp before you touch anything. If you can still re-record, a step back from the mic or a darker microphone may solve what an hour of EQ cannot.

In the mix, harshness usually sits in the upper mids, very roughly between 2 and 5 kHz, where our ears are most sensitive. Sibilance, the hissing "s" and "sh", sits higher. The real trap is stacking: a bright mic, an "air" boost, heavy compression, saturation and a bright reverb each add a little edge, and together they hurt.

Taming harshness and sibilance

• De-ess early. Put the de-esser before anything that adds brightness. Set it while listening in the full mix, not only in solo. The "s" should get softer, not turn into a lisp.
• Use dynamic EQ for loud notes. If the vocal only stings on the big chorus notes, a dynamic cut that reacts to those moments keeps the rest of the performance bright and alive. A permanent wide cut makes the whole vocal dull.
• Cut narrow resonances. Some voices or rooms have one piercing spot. A narrow, moderate cut there is better than lowering the entire top end.
• Fix the worst moments by hand. Lower the volume of individual "s", "t" and "ch" sounds directly on the clip. It takes ten minutes and sounds more natural than any processor pushed hard.
• De-ess the effects too. Sibilance that goes into a reverb or delay gets spread out and repeated. De-ess the send, not only the vocal.

Whatever you change, compare before and after at the same loudness. A louder version always seems better for a few seconds, and that trick has ruined many mixes.

An order that saves time

1. Balance the faders with no plugins at all.
2. Do the mute test and fix the arrangement.
3. High-pass the parts that don't need lows.
4. Cut problem areas and resonances.
5. De-ess, then control dynamics.
6. Only now add tone boosts you still want.
7. Check quietly, in mono, on a phone and next to a reference.
8. Take a break and listen again with fresh ears.

When the problem is bigger than the mix

Mastering will not rescue a muddy or harsh mix. A mastering engineer works on the stereo file, so problems in the balance go into the master with it. If you still hear the issue after all of the above, get a second pair of ears or hand the mix to an engineer.

Make that handover easy: clearly named stems, your rough mix, a reference track and a few honest sentences such as "the vocal hurts on the high notes in the second chorus". Describing what you hear is more useful than guessing which plugin is wrong.