What is EQ? When and why do we use it?

What is EQ? When and why do we use it? How can it change the sound of a single instrument or a full mix?

Everyone has looked at a stereo system or a digital music player and seen the controls for bass and treble. These are very basic equalization controls or what we usually call EQ.

EQ is one of the most basic sound processors. A one that is available even in the simplest car sound systems. But when we create music, we use much more elaborate and precise EQ tools.

In this episode we’re going to talk about what we do with EQ and why we use it in music. We use a key to control the frequency spectrum of a piece of audio.

But what is frequency?

It’s a function of air vibrations. For example; When you pull a guitar string, it vibrates and creates rapid changes in air pressure. Or what we call sound wave. The number of sound wave cycles per second is the frequency of the string and we measure it in units of Hertz.

The frequency is what determines the pitch at the end of hearing. The human frequency hearing range is approximately 20 Hertz to 20 kilohertz. It differs from one person to another. Depending on age, ear structure and how many loud parties you’ve been to 🙂. So just you know certain animals hear different frequencies. Dogs for example can hear up to 45 kilohertz 🐶.

Now back to music. Every instrument plays a certain range of frequencies, that defines its sound. And along with other elements like timbre, distinguishes it, from other instruments.

Now I want to you to play a few samples of different instruments. And we’re going to look at an EQ plug-in called HEQ. Which has a spectrum analyzer. So you can see where the frequency range of each instrument flies. A spectrum analyzer is a graphical representation of the sound that we are hearing.

Let’s start with a kick drum… Which is usually the biggest drum in the drum set and as such produces the lowest frequencies.

Now let’s hear a snare drum… Whose frequency lies more in the mid range.

And here are the symbols… Which take up mostly the high frequencies.
For our last instrument example.

Let’s hear a piano… which covers a wide range of frequencies.

Now let’s hear what happens when we change the EQ of different instruments…

So far we’ve been listening to individual instruments. Now let’s see what happens when we change the EQ of a full mix…

Let’s take the same example as we just did with the bass and cymbals. And apply them to the song called Piano Session #1 by the artist Benjamin’s Brother

Notice how it sounds when you raise or lower the low frequencies. This is the same effect that happens as moving the bass knob on your stereo.

When you raise or lower the high frequencies. This is the same effect as moving the treble knob on a stereo or car radio. That’s basically how it works.

So we’ve heard what EQ does. But why exactly do we use EQ when making or mixing music? Well we don’t always want the full frequency range of every instrument in our mix. EQ can help us sculpt the sound image, boost what’s desired and cut what is not.

With EQ, you can bring the best out of each instrument. Make sure that different instruments don’t clash and muddy up the overall sound. And finally you can use EQ to add the right colour to your music, set the right mood. What I would call the artistic side of EQ.

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