Tools for Mixing: EQ, part 1
By Ernie Rideout
For a songwriter or a band, is there anything more exciting than having finished recording all the tracks for a new song? Hardly. The song that existed only in your head or in fleeting performances is now documented in a tangible, nearly permanent form. This is the payoff of your creativity!
Assuming that all your tracks have been well recorded at fairly full levels, without sounds that you don’t want (such as distortion, clipping, hum, dogs barking, or other noises), you’re ready for the next stage of your song’s lifecycle: mixing.
If you haven’t mixed a song before, there’s no need to be anxious about the process. The goal is straightforward: Make all of your tracks blend well and sound good together so that your song or composition communicates as you intended. And here at Record U, we’ll show you how to do it, simply and effectively.
Regardless of whether you’ve recorded your tracks in computer software or in a hardware multitrack recorder, you have several tools that you can use to create everything from a rough mix to a final mix.
Faders: Use channel faders to set relative track levels.
Panning: Separate tracks by placing them in the stereo field.
EQ: Give each track its own sonic space by shaping sounds with equalization.
Reverb: Give each track its own apparent distance from the listener by adjusting reverb levels.
Dynamics: Smooth out peaks, eliminate background noises, and bring up the level of less-audible phrases with compression, limiting, gating, and other processes.
As you learn more about mixing here at Record U, you’ll learn how these tools interact. This article focuses on the most powerful and — for those new to recording, at least — the most intimidating of them: EQ.
In fact, in the course of this article we’re going to create a mix using nothing but EQ, so you get comfortable using it right away. But before we go on, we must make you aware of its main limitations:
- It cannot improve tracks that are recorded at levels that are too low.
- It cannot fix mistakes in the performance.
Hopefully you’ll discover that EQ can be a tremendously creative tool that can improve and inspire your music. Let’s see how it works.
What is it we're mixing?
Before we start tweaking EQ, let’s look at exactly what it is we’re trying to blend together, which is essential to understanding how EQ works. Let’s say we’re going to mix a song consisting of drum, electric bass, electric guitar, organ, and female vocal tracks — a very common configuration. Let’s focus on just one beat of one bar, when all that’s happening is the bass and guitar playing one note each an octave apart, the organ playing a fourth fairly high up, the vocalist sustaining one note, and the drummer hitting the kick drum and hi-hat simultaneously. Here are the pitches on a piano keyboard:
Fig. 1. Here are the fundamental pitches occurring on one beat of our hypothetical multitrack session. Kick drum and hi-hat are dark blue, the bass is red, the guitar is blue, vocals are yellow, and the organ notes are green. With all the space between these notes, what could be so hard about mixing these sounds together?
Let’s take a different look at the fundamental pitches of our hypothetical multitrack moment. In this diagram, the musical pitches are expressed as their corresponding frequencies.
Fig. 2. Here are the fundamental pitches of our hypothetical recording session again, this time displayed as frequencies on a logarithmic display. New to logarithmic displays? The lines represent increases by a factor of 10: To the left of the 100 mark, each vertical line represents an increase of 10 Hz; between the 100 and 1k mark, the vertical lines mark off increases of 100 Hz; between the 1k and 10k mark, the increases are by 1,000 Hz; above 10k, the marks are in 10,000 Hz. This is to accommodate the fact that each note doubles in frequency with each higher octave; the frequencies add up fast over an eight-octave span. No matter how you count , it still doesn’t look like this would be tough to mix. Or does it?
Ah, if only that were so. The fact is, one of the reasons that music is so interesting and expressive is that each instrument has its own distinctive tone. You can see why some instruments sound unique: Some are played with a bow drawn across strings, others have reeds that vibrate when you blow into them, some vibrate when you hit them, and others make their sound by running voltage through a series of electronics. But why would that make a group of instruments or human vocalists any harder to mix?
Instruments sound different because the notes they make contain different patterns of overtones in addition to the fundamental frequency: Each instrument has its own harmonic spectrum. Sometimes the overtones are not very loud and not numerous; with some instruments the overtones can be just as loud as the fundamental, and there can be upwards of a dozen of them. Let’s take a closer look at the notes of our hypothetical recording session, this time with all of the overtones included.
Fig 3. Here’s what the harmonic spectrum of that single bass guitar note looks like.
Fig 4. The harmonic spectrum of our electric guitar note might look like this — and this is through a clean amp!
Fig. 5. The fourths the organ player is holding yield a harmonic spectrum that’s even richer in overtones than the guitar.
Fig. 6. Though they’re not necessarily tuned to a particular pitch, the kick drum and hi-hat have a surprising number of overtones to their sound.
Fig. 7. If our vocalist sings an “oo” vowel, her note will have the overtones in yellow. If she sings an “ee” vowel, she’ll produce the orange overtones.
Fig. 8. Let’s put the whole band together for our hypothetical one-note mixing job. Yikes. That’s a lot of potentially conflicting overtones, and none of the tracks are even similar to each other in tone! It looks like this is going to be one muddy mix, unless we apply some EQ!
It seems that our simple hypothetical multitrack mix assignment might not be so simple after all. All of those overlapping overtones from different instruments might very well lead to a muddy, indistinct sound, if left alone. Fortunately, even a seemingly cluttered mix such as this can be cleared up in a jiffy by applying the right kind of EQ techniques.
There are several types of EQ, each of which applies a similar technique to achieve particular results. However, the terms that you may hear or read about that describe these results can vary widely. You’ll often hear the following terms used, sometimes referring to particular EQ types, at others referring to generic EQ applications.
- Carve out
As we go through the various types of EQ, we’ll define exactly what these terms mean and get you acclimated to their usage. We’ll also illustrate each EQ type with audio examples, harmonic spectra, and plenty of sure-fire, problem-solving applications.
Part 2a - Tools for Mixing: EQPart 1 - Recording Guitar