Music producers build complex arrangements using synthesizers, found sounds, acoustic instruments, and vocals, often layering them on top of each other. Sometimes, the result is almost perfect. Other times, unwanted resonances build up and ring out.
Mindlessly isolating each frequency in a parametric EQ plugin to find the one causing the issue can drive even experienced mixing engineers mad. But between the extremes of cacophony and a lifeless mix lies a happy middle — and the path to it runs through understanding the relationship between pitch and frequency.
What is pitch?
Pitch isn’t a concept only singers should worry about: it’s a perceptual tool all musicians use to label notes across all octaves.
Each musical note is assigned a specific pitch. For example, the note A above middle C is commonly referred to as A4.
On a piano, each key is a semitone (or half step) away from the next. On a guitar, frets guide the player in a similar way. But when it comes to singing or playing instruments like the violin, we rely on hearing and muscle memory to land on the intended pitch.
This is what makes some arranging and mixing tasks more complex than others. For an arrangement to sound harmonious, all layers must be in tune relative to one another.
For example, it’s typical for a symphony orchestra to tune to the oboe playing a steady A4, since it produces a clear, stable tone that’s easy to match. In electronic music, it’s the producer’s job to maintain that same level of tuning awareness in the instrumentation.
Pitch deviations
The best way to measure how far a monophonic sound deviates from the pitch centre is with a tuner or pitch correction tool.
In tuning plugins, each semitone is divided into 100 cents. For instance, if you see +11ct when you click on a pitch in a plugin like Melodyne, it means the note is 11 cents sharp. It’s a barely noticeable deviation, and lowering the value to 0ct would tune that pitch to perfection. But there are multiple scenarios in which perfect pitch doesn’t work.
In a jazz band, an upright bass may naturally drift around the pitch centre. A string quartet may sound harmonious together, but clash with the synth layers added later in a production.
Most sound sources consist of multiple frequencies, which is what gives them their distinct timbre or sonic character. So, when making tuning decisions, we subconsciously prioritise the fundamental frequency, which is often the loudest perceived pitch.
But there is one sound source that generates a single frequency with each note you play: the sine wave, which lives in most additive, FM, and modular synthesizers. In other words, a sine wave produces only one audible pitch.
Here’s how a sine wave compares to other sound sources playing the same pitch.
What is frequency?
Frequency in music refers to the rate of vibration of a sound wave, measured in Hertz (Hz), which determines the perceived pitch of an instrument or voice.
Pitch is useful for describing musical notes at various registers. Frequency, on the other hand, is a numerical measurement, closer to mathematics than musical language.
Some frequencies correspond to a semitone, while others fall somewhere in between. Luckily, there are parametric EQ plugins like FabFilter’s Pro-Q 4 that display not only each audible frequency, but also their relationship to the nearest semitone in cents. This makes pinpointing resonances that feel out of tune easier.
Still, knowing the basics of the formula can be useful. For instance, a sine wave at 440 Hz corresponds to A4. The same pitch, an octave higher, appears at 880 Hz, while A3 sits at 220 Hz.
It’s the combination of multiple frequencies at different amplitudes that gives each sound its distinct timbre.
Let’s put it to the test. Here, we have a vocal sample from my BandLab Sounds pack, SIRMA Presents Ethereal Pop Vocals: a single syllable sung in C4. First, you’ll hear how it compares to a sine wave playing the same pitch. Listen to what happens when we isolate the fundamental frequency in the vocal sample using the Brickwall setting, which is a steep filter, in Pro-Q 3.
All of a sudden, it’s nearly impossible to distinguish the vocal from the sine wave.
This is why it’s important to respect the frequency content that makes up the timbre of a sound while producing music. With parametric EQ plugins, it’s easy to reduce or remove specific frequencies. But doing so may strip a sound of its character.
Harmonics / Overtones
When a sound lacks sonic character, producers often turn to saturation or distortion to introduce harmonic excitement. These effects generate additional frequencies by reshaping the waveform, which are commonly referred to as harmonics or overtones.
In physics, a harmonic is an exact multiple of the fundamental frequency, whereas an overtone can be any frequency above it. But musicians generally use these terms interchangeably.
Although it’s impossible to predict every overtone without a spectrum analyser, you can expect to find a specific series of harmonics for each pitch. These harmonics appear at fixed ratios, though their amplitudes vary depending on the source and its timbre.
For practice, let’s revisit the same vocal sample singing C4.
The fundamental frequency, also known as the first harmonic, is C4 at approximately 261 Hz.
The second harmonic is C5 at approx. 523 Hz.
The third harmonic is G5 at approx. 785 Hz.
The fourth harmonic is C6 at approx. 1046 Hz.
Because each harmonic is a multiple of the fundamental frequency, its intervallic relationship establishes musicality within a single pitch. The less crowded the overtones are, the purer the perceived pitch becomes. Too many inharmonic or dense overtones result in what we perceive as noise.
Rethinking your EQ decisions
Now that you understand the relationship between pitch and frequency, you can make smarter EQ decisions.
For example, certain harmonics in melodic instruments may sound atonal relative to the key your arrangement is in, especially when they dominate the fundamental frequency. In these cases, you can shape the layers in the instrumentation with this interaction in mind, or use EQ to tame problematic resonances.
But it’s essential to keep the risk of going overboard in mind. If you solo a vocal take and focus too closely on individual overtones, you’re likely to do more harm than good. Take breaks and regularly check each layer in the context of the full mix.
And remember: every time you make a sharp EQ cut, you shift the balance, giving more prominence to surrounding frequencies. Bypass the EQ to observe the effects of your changes at each step to maintain objectivity and avoid ear fatigue.
SIRMA is an Istanbul-born, New York-based artist, songwriter, and producer. With her distinctive vocal textures, she bends her sound across genres—from pop and electronic to ambient and cinematic soundscapes. Outside the studio, she writes for MusicTech and Roland Articles, diving into the creative and technical sides of music production.
