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Understanding Basic Chord Composition Music Theory: A Simple Introduction

By Bobby Kittleberger


Of all the instruments (outside of drums and percussion) guitar might be the one that tempts us the most to fudge on our music theory.

Because we don’t really need it to play.

In fact, there’s a lot you can accomplish on a guitar that requires little or no music theory. Take guitar chords for example.

Most of us know how to play them - perhaps many of them - but we don’t actually understand what they are or how they function in the theoretical realm. And in a way, that’s alright. You don’t need to look at every aspect of what you’re doing on the fretboard with music theory-lenses

Sometimes it’s good to just pick up and play.

But at some point, it helps to know the background and the concrete terms that allow you to describe what your fingers are doing.

We’ll do just that by looking at the theoretical specifics of chord composition, a small and easily understood piece of the music theory puzzle.

What exactly is Chord Composition?

Chord composition is how you would describe the terms given to different pieces and aspects of a given chord.

If you’ve already learned a C chord, that “C” letter is an aspect of the chord’s composition, namely, the root note. So knowing chord composition means you know the different parts of a chord, how to write them out and how to articulate them.

There are four such parts that you need to know and that we’ll cover here:

  1. Root Note
  2. Chord Quality
  3. Interval Number
  4. Additional Interval Numbers (added tones)

We’ll cover each one of the pieces, beginning with the easiest - and most obvious - the root note.

Quality #1: The Root Note

Every chord comes from a scale, meaning that a seven note scale provides us with seven basic chords within that scale.

Thus, each degree of a given scale (1st, 2nd, 3rd, etc.) becomes the root of its own chord.

That scale degree is where we get our root note or the chord’s “tonic.” In other words, when we have a “E” chord, it’s referred to as such because it has been built on an E note and fits within a corresponding scale.

On the guitar, that root note will, generally, be the lowest note in a chord and will be the same note as the chord’s tonic.

Take our E chord for example:


The root note is easily identified on the sheet music and tab as the lowest E note in the chord, thus the tonic of the chord’s scale degree.

A simpler way to think about it is that the chord gets its letter value from the key that it represents.

You might write it out like this:

Root note = Tonic of Scale Degree = Chord’s Letter Value

2. Chord Quality

You’re likely to be familiar with the terms “major” and “minor” chords. You might even know what they mean, in terms of how they make a chord sound.

In general, major chords sound happy or positive, while minor chords sound dark and brooding.

The chord quality can be more accurately defined as the component intervals that define the chord, where intervals are notes that fall a certain distance from the chord’s root note. Different combinations of intervals create different chord qualities.

There are five main qualities that you could run into:


  • Major
  • Minor
  • Augmented
  • Diminished
  • Half-Diminished


The sets of intervals that make up these qualities will vary, but it’s good to know their titles and know that they’re based on intervals, as they relate to the chord’s root note.

Let’s take a Caug (augmented) chord for example:


Our root C is the note at the third fret (the lowest one in the diagram) while our augmented fifth is seen at the first fret on the third (G) string.

If we know that the interval from C to G is a perfect fifth - or seven semitones - we can memorize that an augmented fifth would be C to G♯ or eight semitones.

By analyzing intervals in this manner, you’ll be able to determine chord quality.

Or you can at least know the why and how behind the naming convention. Next time you see a minor chord, you’ll know it possesses that quality because of a minor interval, relating to the root note, which is related to a sequence within a particular scale.

It all fits.

3. Interval Number

An interval number shows up when you have an additional interval that adds a tone to the interval that creates a chord quality.

If we stick with our Caug from above, a corresponding example would be Caug7.

That “7” is our interval number, meaning we would need to add one more notes to our chord in order to complete it. The three we have in the original Caug isn’t enough. If we know our intervals , we can deduct that a major and minor seventh is 11 and 10 semitones from the root note, respectively.

If we go with the minor seventh interval, that adds a Bâ™­ to the chord.

That shape is easier to achieve if we move the root note to the eighth fret. The program I used to make the chord returned a slightly different naming convention, but the principal is the same.


4. Additional Interval Number: Added Tone Chords

The fourth and final aspect of chord composition that we’ll cover is an added tone, or simply another interval that’s denoted in the chord’s title.

This will show up as add9, add13 or similar indicators, depending on the number of the interval.

You need to have what’s called a tertian-triad already in place before you can have this extra “added” note. That tertian-triad, in our example, would be the interval explained in step number three. The added tone then cannot be part of the sequence of thirds from the root note.

In other words, it must be outside of the triadic interval sequence. Second, fourth, ninth and 13th are just a few example.

But when you see that add9 or similar naming, you’ll know that it’s because of the following:


  • The chord has an additional added tone.
  • The extra interval is not part of the triadic sequence.
  • This note does not change the quality of the chord.


And that’s all there is to it folks.

Theory is not easy. In fact, I’ve always felt that even the “easy” parts of theory are hard to grasp, that is, without taking just a little bit at a time.

So my advice is to refrain from biting off more than you can chew.

Stick to small chunks like this and introduce new concepts as you’re comfortable.

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