Inversions And Bass Lines

Chords can be placed in inversion, which means that they have a note other than the root in the bass. These inversions (particularly second inversion, in which the fifth appears in the bass, or third inversion, in which the seventh appears in the bass) can sound weaker than chords in root position, but they can still be useful in specific contexts. 

The chords we’ve studied so far have been in root position, which means that the root, or main note, of the chord is also the lowest note. An inversion occurs when the bass is a note other than the root.

(Students frequently struggle with the differences between the words “tonic,” “root” and “bass.” Tonic means the main note of a key. Root is the main note of a chord. The bass is the lowest note of a chord, even if that note isn’t the root.)

Sometimes, it can be effective, or even necessary, to place a note other than the root in the bass – doing so can create a richer, more complex chord voicing, or a more pleasing melodic motion in the bass line.

The connecting thread of this chapter, in fact, is that chord inversions can help you write smoother, well-executed bass lines. In particular, by using inversions, you can write bass lines built more on steps, rather than on leaps. There is no problem with writing bass lines that contain leaps (and in some genres of music, like punk, we might simply want to have the bassist play roots the vast majority of the time). But sometimes, a bit more motion by step can help the bass line sound more like, well, a line, rather than just a series of roots.

In pop and jazz notation, inversions are indicated with a slash. The chord name comes before the slash, and the bass note comes after it. For example, “C/G” means to play a C major chord with a G in the bass.

Here are a few more examples.

Am/C: An A minor chord (A, C, E) with a C in the bass
DM7/F#: A DM7 chord (D, F#, A, C#) with an F# in the bass
G7/F: A G7 chord (G, B, D, F) with an F in the bass

A chord (whether it be major, minor or another type) is in first inversion when the third of the chord is in the bass, and second inversion when the fifth is in the bass. So if we see “C/E,” that means that E, the third of the chord, is in the bass, and the chord is in first inversion. C/G (which has G, the fifth, in the bass) is in second inversion.

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Seventh chords are in first inversion with the third of the chord in the bass, in second inversion with the fifth in the bass, and in third inversion with the seventh in the bass. Since plain old triads don’t have a seventh, they don’t have a third inversion. Only seventh chords do.

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Quick Quiz 6.1

What are the inversions (first, second or third) of these chords?

F/C                                     Bb7/D
A7/G                                    Eb7/Db

If you’re a bassist, you’re probably already aware of how different G/B, for example, can sound compared to G. But if you play a different instrument, that might not be so obvious. “They’re both G chords,” you might think. “What’s the difference?”
True, they’re both G chords. And in some contexts, they might sound similar. But in others, the difference between them can be substantial.

Take, for example, the chorus to Chicago’s “You’re The Inspiration.” (We’re going to analyze this song more thoroughly later and will discuss this passage in the key of D# major, for reasons I hope will be clear. For now, we’ll look at it in the enharmonically equivalent key of Eb major, which is easier to deal with.)

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We head here from a  to a first-inversion I chord to IV (Ab). Listen to the way the Eb/G chord creates a sense of forward momentum to the progression. The G in the bass is just below Ab, so it pushes our ears toward the Ab chord that follows. Here’s an outline of the bass line.

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I followed by I in first inversion followed by IV is, in fact, a very common progression – the chorus of Michael Jackson’s “Man in the Mirror,” for example, also uses this device.

Returning to the “You’re The Inspiration” example, notice the Eb/Bb chord, which is an Eb major chord in second inversion.

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Second inversion chords are less common than first inversion because they frequently sound weak and unsettled. What Chicago does here, though, with a I chord in second inversion followed by a V chord in root position at the end of a phrase, is one of the most common uses of the second inversion chord. Note that the Eb/Bb chord really doesn’t feel like an Eb chord; instead, it feels like an embellishment of the Bb chord that follows it. (Music theorists call this I chord in second inversion a “cadential six-four” chord. They’ll think you’re super cool if you use this term correctly.)

Another common use of the second inversion chord occurs when there is a passing motion in the bass — that is, when a second inversion chord arises as the result of the bass line moving up by step or down by step.

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In the example above, the bass moves from D up by step to E, then up by step again to F#. The middle chord is therefore an A major chord in second inversion. The chord doesn’t sound weak or unsettled, though, because of the bass line is smooth.

We can also sometimes use second inversion chords when doing so allows us to retain the same note in the bass. Here’s an example.

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Here, the G/D in the middle (a G major chord in second inversion) works well because it allows us to keep the D in the bass line, which also fits the chords on either side of the G/D.

Third Inversion Chords

Like second inversion chords, third inversion chords are unstable and shouldn’t be used at random. We mostly just want to use them when there’s a descending motion by step in the bass line. The first verse of Elton John’s “Your Song” demonstrates this principle.

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The second chord in m. 3 above is a C minor chord in third inversion – C minor with a Bb in the bass. The chord sounds unstable, but our ears can make sense of its instability because of the passing motion in the bass line. Here’s an outline of the bass line beginning at measure 3.

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The Bb in the cm/Bb chord allows the bass to pass smoothly from C to A natural (and then on to Ab).

Third inversion chords will frequently work well in these sorts of descending bass lines. To create one, begin with a stable chord, like the C minor in the Elton John example, and head down from there.

Constructing A Bass Line

Let’s imagine we’re writing a song with a fairly straightforward chord progression in the key of D.

D / A / | Bm / G / | D / G / | A / / / |

It will certainly sound fine to simply have the bass play roots throughout.

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However, let’s try to spice up our bass line by using inversions to create a bit more stepwise motion.

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Whether you prefer the first bass line or the second is a matter of taste, but hopefully it’s clear how inversions can change things. In the bass line with inversions, we added an A/C# chord (that is, a first inversion A major chord) to allow the bass to descend by step. Then, we added a D/F# chord at the beginning of the third measure, mostly to counter the large leap up from B to G that preceded it. It’s often a good idea to follow a large leap with a step in the opposite direction.

Next Chapter: Chords In Minor Keys

Quick Quiz Answers

6.1
F/C = 2nd inversion
A7/G = 3rd inversion
Bb7/D = 1st inversion
Eb7/Db = 3rd inversion