A spectrum analyser shows you the frequency content of an audio signal in real time. The horizontal axis represents frequency (low to high, left to right), and the vertical axis represents amplitude (how loud each frequency is). It is one of the most useful tools in music production, but only if you know how to read it.
The basics
The display shows a curve that moves in real time as audio plays. Every bump in the curve means there is energy at that frequency. The higher the bump, the louder that frequency is in the signal.
Most spectrum analysers use a logarithmic frequency scale. This means low frequencies get more visual space than high frequencies, which matches how human hearing works. On a linear scale, everything above 1 kHz would be crammed into the right side of the display and you would not be able to see detail in the low end.
The amplitude axis is usually measured in decibels (dB). A difference of 6 dB means one frequency is roughly twice as loud as another. A difference of 20 dB means one is ten times louder.
What the frequency ranges mean
Here is a rough guide to what lives where:
20-60 Hz (Sub-bass) — The lowest frequencies. You feel these more than you hear them. Sub-bass rumble, kick drum fundamentals, 808s. Too much here and your mix sounds muddy and uses up headroom. Too little and it sounds thin on big systems.
60-250 Hz (Bass) — The body of your kick drum, bass lines, and the low end of synths. This is the power zone in hard dance. Getting this range right is the difference between a kick that hits and one that just exists.
250-500 Hz (Low-mids) — The "mud" zone. Energy buildup here makes mixes sound boxy and unclear. Cuts in this range often clean up a mix more than boosts anywhere else.
500 Hz - 2 kHz (Mids) — The body and tone of most instruments. Vocals, synth leads, and the tonal character of kicks live here. This range defines how "full" your mix sounds.
2-6 kHz (Upper-mids/Presence) — Human hearing is most sensitive in this range. This is where clarity, bite, and aggression come from. Screech leads, distorted kicks, and vocal presence sit here.
6-12 kHz (Brilliance) — Air, shimmer, and the top end of cymbals and hi-hats. Too much and the mix sounds harsh. Too little and it sounds dull.
12-20 kHz (Air) — Very high-frequency content. Most of this is harmonics and noise. Some people cannot hear above 16 kHz. Gentle presence here adds openness.
Reading the curve shape
A well-mixed track does not have a flat spectrum. Different genres have characteristic shapes:
In hardstyle and rawstyle, you will see a large hump in the 40-150 Hz range (the kick), a dip in the 200-400 Hz range (the pocket between kick and mids), energy in the 2-5 kHz range (lead synths and kick top-end), and a roll-off above 10 kHz.
The spectrum should not have any sharp, narrow spikes that stick out far above the surrounding frequencies. Those are resonances, and they usually indicate a problem — a ringing frequency in a synth, a room mode in a recording, or feedback in a reverb.
Block size and resolution
The FFT (Fast Fourier Transform) block size determines how detailed the analysis is. A larger block size gives you better frequency resolution (you can see individual notes in the bass range) but worse time resolution (the display reacts slowly to changes).
- 1024 samples — Fast response, low frequency detail. Good for watching transients and rhythmic content.
- 4096 samples — Balanced. Works for most mixing and mastering scenarios.
- 8192-16384 samples — High frequency detail, slow response. Good for finding specific resonances or analyzing sustained sounds.
For hard dance production, a block size of 4096 is a solid default. You get enough low-end resolution to see what your kick is doing while still being responsive enough to track the rhythm.
Pre/post and A/B comparison
Most spectrum analysers let you place them at different points in the signal chain. Use this to your advantage:
- Pre-EQ vs post-EQ — See exactly what your EQ is doing by comparing the spectrum before and after.
- Pre-limiter vs post-limiter — Watch how the limiter changes the spectral balance. Heavy limiting often boosts perceived midrange.
- Your mix vs a reference — Load a reference track into the analyser and overlay it with your mix. The difference in shape tells you exactly what tonal adjustments your mix needs.
This last technique is extremely valuable. Instead of guessing whether your low end is right, you can see it compared to a track you already know sounds good on big systems.
Common mistakes when using analysers
Mixing with your eyes instead of your ears. The analyser is a verification tool, not a mixing tool. Make decisions with your ears first, then check the analyser to confirm. If the analyser says something is "wrong" but it sounds right, trust your ears.
Obsessing over flatness. Music is not supposed to have a flat spectrum. A flat spectrum sounds clinical and lifeless. The spectrum should match the genre and the intent of the track.
Ignoring the time domain. A spectrum analyser shows frequency content but not timing. Two mixes can have identical spectrums but sound completely different because of transient shapes, groove, and dynamics. The spectrum is one dimension of many.