Identifying Frequency Bands Guide

Why This Matters

The audio industry is rife with imprecise vocabulary. Terms like "muddy," "warm," "crisp," and "airy" populate mixing forums and studio conversations, yet these words carry different meanings for different listeners. This ambiguity makes professional communication difficult and slows the development of critical listening skills.

The alternative is to describe sound in terms of its physical properties. When you can identify that a vocal has excessive energy between 200 and 400 Hz, you communicate something precise and actionable. The engineer receiving that note knows exactly what to address. This precision is the goal of frequency band training.

William Moylan, in his book Understanding and Crafting the Mix, argues that we must develop what he calls "reference experiences" for each frequency region. These internal references become the measuring stick against which we evaluate all subsequent sounds. The tool on this page is designed to help you build those references.

The Frequency Bands

This tool divides the audible spectrum into six regions based on Moylan's framework (see Chapter 4, page 106). The boundaries align with musical pitch rather than arbitrary round numbers.

Band	Range	Character
Low	Up to 65 Hz	Sub-bass, felt more than heard. Kick drum fundamentals, bass synth sub-octaves.
Low Mid	73–196 Hz	Bass guitar fundamentals, lower piano notes, male vocal chest resonance.
Mid	220–440 Hz	Body of most instruments. Where "boxiness" and "muddiness" often reside.
Mid-High	494–1319 Hz	Vocal presence, guitar attack, snare body. The "telephone" range.
High	1397–4186 Hz	Vocal clarity, consonants, hi-hat stick definition, string "bite."
Very High	4186 Hz and above	Air, shimmer, cymbal wash, breath sounds, tape hiss.

These boundaries are not sacred. Different engineers and textbooks use different divisions. The value lies not in memorizing these exact numbers but in developing sensitivity to the qualitative differences between regions.

How to Use the Tool

Audio Source

The tool offers three source options:

Mute: No audio output. Use this when adjusting settings.
Pink Noise: A signal with equal energy per octave, making it ideal for calibrating your ears to each band in isolation.
User Audio: Upload your own music to analyze real-world frequency content.

The gain slider adjusts output level from -70 dB to +6 dB. Start at a comfortable listening level (around -12 dB) and avoid fatiguing your ears with extended loud listening.

Frequency Band Controls

Each of the six bands has two buttons:

M (Mute): Removes that frequency band from the output.
S (Solo): Isolates that band so you hear only its content. Multiple bands can be soloed together.

The "Filters On/Off" toggle enables the Mute and Solo controls. Audio passes through unaltered until you actually mute or solo a band, so there is no coloring from the filter network when all bands are active.

User Audio Controls

When "User Audio" is selected, the audio player controls become active. There are two players: Audio 1 is the primary player, and Audio 2 (collapsed by default, click the arrow to expand) lets you load a second file for A/B comparison. Only one player can play at a time: pressing play on one automatically pauses the other.

Each player provides:

Play/Pause: Start and stop playback. The space bar toggles the most recently used player.
Waveform: Shows the audio waveform with playback position highlighted. Click anywhere to seek.
Loop: Enable looping and drag the handles (or type times) to define a loop region.
Upload: After loading a file, a small upload icon on the right lets you swap in a different file.

Hover over the i buttons next to each control section for additional information.

Demo Mode

The "Run Demo" button cycles through each frequency band, soloing them for three seconds each. This provides a quick survey of the entire spectrum and is useful for initial calibration.

The Exercise

This exercise follows a two-stage structure: calibration with pink noise, then application to music.

Stage 1: Calibration

Before analyzing music, establish your reference experiences using pink noise.

Select "Pink Noise" and set a comfortable listening level.
Solo each frequency band in sequence, spending at least 30 seconds with each.
For each band, ask: What is the physical sensation of this frequency region? Where do I feel it in my body? What vowel sound does it resemble?

Pink noise removes the distraction of musical content, allowing you to focus purely on spectral character. This is the "reference experience" Moylan describes.

Tip

Some listeners find it helpful to associate each band with a vowel sound or physical sensation. The Low band might feel like a gentle pressure in your chest; the Mid-High might sound like the "eh" in "telephone."

Stage 2: Application

Switch to "User Audio" and upload a reference track (the same one you analyzed in previous exercises works well).

Enable the loop function and select a 15-30 second passage that contains instruments across the full spectrum.
Solo each frequency band and identify what instruments are present in that region.
Note which band contains the most energy from each instrument. A bass guitar will appear in multiple bands, but its fundamental energy concentrates in one or two.

Stage 3: A/B Comparison (Optional)

Expand Audio 2 and load a second track to compare how different recordings distribute energy across the frequency spectrum.

Load two recordings of similar material (two mixes of the same song, or two songs in the same genre).
Solo a frequency band, then switch between the two players to hear how each recording treats that region.
Note the differences: does one mix have more Low Mid energy? Is one brighter in the High band? These observations build the vocabulary described in the section below.

What to Listen For

As you work through the exercise, consider these questions for each frequency band:

Which instruments have their fundamental energy here? (The lowest, loudest pitch of a note.)
Which instruments have harmonic content here? (Upper partials that add timbre and definition.)
What happens to the overall mix when this band is removed?
Are there any frequency buildups or masking issues in this region?

On filter design: The filters in this tool have steep cutoffs that exaggerate the transition between bands, making the boundaries easier to hear. Real-world EQ typically uses gentler slopes.

Building Vocabulary

The goal of this exercise is to replace vague descriptors with precise observations. Instead of saying a mix sounds "muddy," you might identify that the Low Mid band (73–196 Hz) contains excessive energy from both the bass guitar and the low end of the rhythm guitar, creating masking.

Some translations from subjective to objective:

"Muddy" often indicates buildup in the 200–400 Hz range (Mid band).
"Thin" or "tinny" suggests insufficient Low Mid content.
"Harsh" typically points to excess energy in the 2–4 kHz range (High band).
"Dull" may indicate insufficient Very High content or a rolled-off top end.
"Boomy" often lives in the 100–200 Hz range (Low Mid band).

These translations are generalizations. The point is not to memorize them but to develop your own correlations through repeated listening.