One of the most important types of processing in mixing is EQ as this allows you to sculpt the tone of your audio by cutting or boosting certain frequencies. In my many EQ cheat sheets (grab my free ULTIMATE EQ cheat sheet if you haven’t already, by the way), I talk about fundamental frequencies of instruments. With that in mind, I thought I should put together a quick definition of what is a fundamental frequency as it relates to sound and music.
What is a Fundamental Frequency
Fundamental frequency refers to the root/lowest and otherwise “loudest” or peak frequency of a sound.
Virtually every sound you can hear resonates at multiple frequencies within the practical range which the human ear can perceive (which incidentally is roughly 20Hz-20,000Hz).
Regardless, there will always be a particular frequency or frequency range that sound peaks at within that spectrum, and THIS is its fundamental frequency.
I like to cite the acoustic guitar to help illustrate the concept of fundamental frequency. In standard tuning with a 440Hz reference, if we strum the lowest E string (an E2), it will vibrate at 82Hz.
82Hz is that open low E string on the acoustic guitar’s fundamental frequency, but it’s not the ONLY frequency we hear when we pluck that string.
If we look at that audio via a spectral analyzer like the display which comes with my favorite EQ, the FabFilter Pro-Q 3, we’ll see the greatest peak surge at 82Hz (indicating the fundamental frequency), but we’ll also see smaller incremental spikes at each octave (164Hz, 328Hz, etc. – note these are rounded numbers). These are referred to as harmonics, and they’re built into the note and many of them will vibrate on top of that initial fundamental frequency.
We’ll also see and hear bumps at other spots which are unique to playing this note on the guitar, like that 8-10k range where we hear the punchy percussive quality of the string itself.
Why Fundamental Frequency Matters
In mixing terms, it’s important to understand where the fundamental frequency of any track we’re mixing resides as we typically want to preserve or even enhance this frequency to make that track sound its best.
If we cut or otherwise undermine the fundamental of a sound, it will sound weaker and much less effective in the context of our mix.
Even more than preserving or enhancing, we want to make sure that one track’s fundamental doesn’t conflict with another track’s fundamental, as this is one of many ways we get a muddy mix.
This is why we use stereo panning and reverb (and other techniques) to take full advantage of the second and third dimensions of our mix. This helps us keep tracks which rely on the same or similar fundamental frequencies farther apart, leading to a cleaner mix.
A prime example of fundamental frequencies being key in mixing is creating space for the kick by way of the bass.
The kick drum is the anchor of the mix for keeping timing and delivering that powerful low end, but the bass’ fundamental frequencies can overlap and the two will fight for space in the low end mixing (especially considering both tracks should be panned dead center, i.e. on top of one another).
A solution is to identify the fundamental of your kick (by way of a visual analyzer), then use sidechain processing to instruct the bass to duck out at that frequency whenever the kick triggers (see my overview on how to use sidechain EQ).
But there you have it, a fundamental frequency definition and just as importantly WHY it matters in the context of mixing.
Fundamental Frequency Definition
- Fundamental frequency refers to the most prominent frequency or frequency range represented by a sound when it plays.
- Most sound is made up of multiple frequencies in overtones and harmonics, but the fundamental is that lowest, prime frequency which that sound vibrates at.
- In the context of mixing, it’s essential to understand the fundamental frequency of every track in your mix so that you can both preserve it via EQ but keep tracks which feature similar fundamental frequencies farther apart in the mix to avoid conflicts.
- In extreme cases, like the case of kick and bass, you may need to work in some sidechain processing to create space when you can’t otherwise simply use panning or third dimensional adjustments to keep tracks out of each other’s ways to create a cleaner mix.
