Why do my chord voicings sound muddy in the low end?

Why low intervals blur

Every note carries overtones above its fundamental. Two low notes a third apart have overtones only a few hertz apart in the low-mid range, and the ear hears the difference between them as roughness. The ear also separates pitches less finely at low frequencies. The same third played two octaves higher is clear, because its overtones are far enough apart to be heard as two notes.

Wider intervals survive lower down. As a rule of thumb, an octave is clean at any pitch, a fifth holds up through the bass register, a third starts to blur about an octave below middle C, and a second or a cluster needs to stay near middle C or above.

Voicings that stay clear

• Root alone in the bass. If there is a bass instrument, let it own the root and take the root out of the keyboard's left hand.
• Root and fifth, or root and octave, if the low end needs more weight.
• Third and seventh around middle C. These two notes define the chord, and that register is where they read best.
• Spread the chord. An open voicing over two octaves is clearer than the same notes inside one.
• Leave notes out. The fifth adds little; dropping it thins the chord without changing what it is.

Why EQ does not fix it

The mud is two notes interfering, not too much level at one frequency. A cut at 200 to 300 Hz makes the instrument thinner and leaves the clash in place. Revoice first, then equalise what is left.

In Zammoth

Open the MIDI clip in the piano roll, select the low third and press ⇧↑ to move it up an octave. The engineer measures the mix's low-mid build-up as a mud reading and measures which tracks mask which in each band, so it can tell you whether the chord part is the cause before you start cutting. See why a mix sounds muddy for the mixing side of the same problem.