Chords: Structure and Inversions

Let's start with a definition. A chord is several different pitches sounding at the same time (§ 107 and 289). In a melody, you hear the pitches one after another; in harmony, and so in a chord, you hear them together.

Stacked thirds

In its basic form, every chord is built from notes of one scale stacked in thirds (§ 290). With three notes, you get a triad, a three-note chord. With four notes, you get a seventh chord, a four-note chord.

What each note of the chord is called

When the chord is stacked in thirds, its lowest note is the root. The other notes are named after the interval they form with it: the third, the fifth and, in a four-note chord, the seventh (§ 291). Take the chord G, B, D, F: G is the root, B is the third, D is the fifth and F is the seventh.

Here's the important part: these names never change, even when you move the notes around (§ 292). Whether the G sits at the top, in the middle or at the bottom, it's still the root. And a chord is always named after its root, so this is “the G chord.”

Root position and inversions

Now let's look at the bass, the lowest note you hear. When the root is in the bass, the chord is in root position. When another note is in the bass, the chord is inverted (§ 293):

• In first inversion, the third is in the bass.
• In second inversion, the fifth is in the bass.
• In third inversion, which triads don't have, the seventh is in the bass.

So a triad has a root position and two inversions, and a seventh chord has a root position and three inversions (§ 294). Only the bass note decides the position. The order of the notes above it doesn't matter at all.

You now know how to name the notes of a chord and find its position. In the next lesson, we'll sort triads into their four types. But first, a few questions.