Tutorials Audio

Bass and Low End: Writing the Part Everyone Feels

By Infinite Creation · Intermediate · ~16 min

Overview

Low end is the part of a record that people feel rather than hear, and it is the part most likely to be wrong, because judging it requires either an acoustically treated room or a set of habits that work around not having one. It is also two problems that get confused: writing a bass part that belongs with the drums and the harmony, and getting the resulting low frequencies to behave. The writing problem comes first, and a lot of what gets treated as a mix fault was decided when the part was written.

You will need:

Headphones you know well, since most rooms lie about bass and headphones lie consistently
A spectrum analyser, because at these frequencies your eyes are more reliable than a domestic room
Two or three reference tracks whose low end you trust

Steps

Write the bass against the kick, not against the chords

The first question is rhythmic. Where the kick lands and where the bass lands relative to it decides how the track feels, and a bass playing exactly with the kick sounds locked while one playing between kicks sounds mobile. Harmony can be corrected later, and this cannot be corrected in the mix at all.

Decide whether the bass follows the root

Following the root of every chord is the safe option and the reason many progressions sound predictable. Holding one note under a changing progression, or moving stepwise between roots, gives the same harmony a different weight for no extra parts.

Give the kick and the bass different territory

They occupy the same frequency range and cannot both own it. The usual solution is that one takes the very bottom and the other sits above: a deep sustained bass with a kick that has its energy higher up, or a deep kick with a bass whose fundamental is above it. Choosing which is the single most consequential low-end decision in a mix.

High-pass everything that does not need low end

Pads, guitars, vocals and room mics all carry energy below where they contribute anything, and it accumulates. Removing it from every part that is not the bass or the kick makes room without touching either of them.

Check the fundamental is actually there

A bass part written high on a synth may have almost nothing below eighty hertz, which sounds full on headphones and vanishes on a system that can reproduce it. Look at an analyser rather than trusting the room, and know where your lowest note actually sits.

Check it survives small speakers

Phone speakers reproduce nothing below a few hundred hertz, and listeners still hear the bass line, because the ear reconstructs a missing fundamental from its harmonics. If your bass has no harmonic content it disappears entirely. Adding mild distortion generates those harmonics and is why so many bass sounds are saturated.

Compare against references at matched volume

Low end is the area where loudness most distorts judgement, because quiet listening flatters bass-light mixes and loud listening flatters bass-heavy ones. Match levels before comparing, or the comparison tells you nothing.

Verify in mono

Wide stereo bass collapses unpredictably when a system sums to mono, and it still happens on club systems, phone speakers and some broadcast paths. Keeping the lowest octaves centred is the usual insurance and costs nothing audible.

Pro Tips

Most untreated rooms have a peak or a null of ten decibels or more somewhere below two hundred hertz. Moving your head a foot proves it faster than any measurement.
If the bass sounds different every time you sit down, trust the analyser and the references rather than the room.
Saturation on a bass is not a tone choice alone. It is how the part stays audible on speakers that cannot reproduce its fundamental.
A bass part that is hard to mix is often one that was written to play too many notes. Removing half of them is a legitimate fix.

Knowledge Base

The Longer Answer

Two effects explain most of the confusion here: what a room does below two hundred hertz, and how a phone reproduces a note it cannot physically produce.

The missing fundamental

Play a bass note at fifty hertz through a laptop speaker and you still hear the correct pitch, even though the speaker produces nothing at that frequency. The ear infers the fundamental from the pattern of harmonics above it, and the inferred pitch is heard as clearly as a real one.

This is why a pure sine bass disappears on small speakers while a saturated one survives. Saturation adds harmonic content at frequencies the speaker can reproduce, and the listener reconstructs the note from them. It is the strongest practical argument for distorting a bass sound even when you want it to sound clean on a big system.

Why rooms lie about bass

Low frequencies have wavelengths measured in metres, comparable to the dimensions of a domestic room. They reflect off the walls and interfere with themselves, reinforcing at some positions and cancelling at others, and the result is a response that varies by more than ten decibels across the space between one listening position and another.

Treatment helps and requires depth to work at these wavelengths, which is why bass traps are large. Without it, the workable approach is to stop trusting the room in that range: check the analyser, compare against references you know, and confirm on headphones and on a small speaker before deciding the low end is right.

Where This Fits

The bass part is one layer of an arrangement, and Making a Record covers the whole record the part sits in.

FAQ

Q: Should the bass or the kick be louder?
A: The question is usually the wrong one. Decide which occupies the lowest octave and give the other its energy higher up, and the balance between them becomes much easier to set.

Q: Do I need a subwoofer to mix bass?
A: No, and an uncalibrated one in an untreated room can make judgement worse. Knowing your speakers, using an analyser and checking references is more reliable.

Q: Why does my bass vanish on my phone?
A: The speaker cannot reproduce the fundamental and your sound has too little harmonic content above it for the ear to reconstruct the note. Saturation fixes this directly.

Q: Should bass ever be in stereo?
A: Harmonics above roughly one hundred and fifty hertz can be widened safely. The fundamental is best kept centred, because stereo content down there collapses unpredictably when a system sums to mono.

Vocabulary

Fundamental The lowest frequency in a note, which sets its perceived pitch. A bass part written high on a synth may have very little energy at its own fundamental, which sounds full on headphones and thin on a system that can reproduce it.

Missing fundamental The effect where a listener hears the correct pitch from harmonics alone, even when the speaker produces nothing at the fundamental. It is why saturated bass survives on phones and pure sine bass does not.

High-pass filter A filter removing energy below a chosen frequency. Applied to every part that is not the bass or the kick, it clears accumulated low-end energy that contributes nothing.

Mono compatibility Whether a mix holds together when its two channels are summed. Wide stereo content in the lowest octaves can partially cancel, which is why the bottom of a mix is usually kept centred.