Slash Chords (1) Inversion

In Chapter I, we discussed the importance of the bass playing the root note. Without doing so, the sound of the chord changes significantly from its original character. We also explained the notation rule that if you intentionally choose other notes as bass, you should add a “slash” to the chord name and then add the bass note.

The technique of the bass playing notes other than the chord root is called a Slash Chord. We briefly touched on it in Chapter I, and this time, we will delve into it more thoroughly.

The concept “slash chords” encompasses all instances where the bass plays notes other than the root, but the reasons and purposes for why the bass acts independently vary depending on the context. In other words, there are many subcategories within slash chords. This is why there will be three consecutive articles on slash chords!

1. What Are Inversions?

The first instance we’re covering here is the usage of Chord Inversion. An inversion refers to the arrangement where a “chord tone” other than the root is placed in the bass.

If we take the example of a C major chord, placing the 3^rd note, E, or the 5^th note, G, in the bass, results in what are referred to as “inverted chords”. The one with 3^rd set in the bass is called a First Inversion, and the one with 5^th set in the bass is called a Second Inversion. Additionally, the basic form without inversion is called a Root Position.

Notations

In Roman Numeral Analysis, there are actually variations in how chord inversions are notated, with differences based on schools and even across countries. Here I adopt the format occasionally used in relatively casual contents; “/3” and “/5“.

I’ll introduce another famous notation later in this session. For now, let’s focus on learning how to use it in practice.

Effects of Inversion

A chord sounds most stable when Rt is solidly played in the bass. Inversion is a technique that deliberately disrupts this stability to create a new sound.

IIVIIV

For example, consider a simple 1-4-1-4 chord progression. Let’s change the I chord to the “first inversion”. The analyzed chord symbol becomes I_/3.

I_/3IVI_/3IV

The sound becomes unsettled and the stability is reduced. In principle, inversions decrease stability compared to the original form.

Looking at the flow of the bassline, the change in position creates a smooth half-step movement. As a result, the musical mood becomes gentler. The primary purpose of using inversions is deliberately reducing stability and, in many cases, smoothing out the bassline.

2. Creating Smooth Basslines

As you may already understand, the magnitude of the bass movement was confirmed as a significant factor in the perceived “energy” of a chord progression. Then, what if you want chord progressions like I→V or VI_m→III_m but want to keep the bass changes moderate? That’s when slash chords come into play.

Here we have a progression familiar as the classic “Canon in D” by Pachelbel. The chord progression often involves the first inversion to construct a smooth descending bassline:

By having the bass take the 3^rd at key points, we achieve a smooth bassline that looks great anywhere. Such a clean bass flow is always pleasing to the listener.

Let’s compare in a more musical context. First, without slash chords:

It’s not bad as it is, but the bass movement seems a bit too dynamic for a relaxed song. Smoothing out the bass using the first Inversion yields this result:

This arrangement creates a beautiful, smoothly ascending flow up by half-steps until the 6th bar! It sounds incredibly beautiful, matching the song’s pastoral emotions.

Example

“Superstar” by Tokyo Incidents, a Japanese rock band, uses the same chord progression as the example above in the chorus part, gradually ascending by half-steps. It’s a perfect progression for expressing a gentle yet simmering rise of emotions!

3. Third Inversions

In the case of seventh chords, placing the 7^th as the bass note is naturally considered one of the “inversions”, and called Third Inversion. Third inversion is particularly common with dominant seventh chords, for example:

The sounds of third inversions are quite fascinating. Let me introduce some typical patterns.

Third Inversion of V7

Among third inversion chords, that of V₇ will be the most prominent. It often progresses to III_m, III or I_/III with a high probability. The bass descending by a half-step bears the smooth and beautiful characteristic.

IV_Δ7V7III_m7VI_m7

This is a basic 4-5-3-6 progression without any inversion. The bass going up from fa to so produces a mood of rising, the power to move things forward.

IV_Δ7V7_/7III_m7VI_m7

This is the alternative version where the bass remains stationary on fa, constituting the third inversion of V7. While losing some driving force, it gains more melancholy. It’s like the frustrating feeling of trying to move forward while the hem of a long skirt is being stepped on, a sensation akin to stagnation, expressing a mixture of positive and negative emotions. Maybe due to that characteristics, it is often used in slow ballads.

Examples

The chorus part of “I Need To Be In Love” starts with the progresison IVV7_/7III_mVI_m.

“Is This Love” is a similar case—It uses 4-5-3-4 progression, with the V₇ in third inversion. As a result, the bass stays at IV for a longer duration, creating a softly floating mood. With IV set as the bass, the third inversion of V exudes a unique beauty, seemingly residing somewhere between dominant and subdominant function.

Third Inversion of I7

I7/7 if often followed by IV/3 as it forms a smooth ti♭-la bassline.

You might have heard this kind of usage in lively pop music. Pay attention to how smoothly the bass moves by a descending step line. By utilizing multiple inverted chords you can make elegant basslines with various chord choices.

4. I/3 or IIIm, That is the Question

The inverted chord most frequently used is likely to be “I/3”, which has already appeared multiple times in the above samples. This chord has some similarities to IIIm in terms of chord tones.

Of course, the difference lies in whether the note do is included. However, this difference is significant, leading to opposite directions in sound, whether it’s a very unstable tendency tone ti or the stable tonal center do.

III_mIVVVI_m

Here is a simple progression of 3-4-5-6. Due to the inclusion of the note ti, the atmosphere becomes dark and stagnant from the beginning.

I_/3IVVVI_m

Here is the version where the beginning is I/3. By not including the note ti and instead highlighting do, it pushes the impression of a bright tonic start. The sound changes significantly, creating a sense of overflowing hope or joy.

So, even if you casually use I_Δ7 most of the time, when using I/3, sometimes it’s better not to incorporate the note ti, so you need to pay attention. Paying attention to such details and pursuing the best-fit sound can lead to a big difference!