Ab7b5 Piano Chord

Piano Diagram of Ab7b5 in Root Position

Ab7b5 is a dominant seventh chord with a flat 5th built on the Ab major scale. This chord consists of the root note Ab, the major third C, the diminished fifth Ebb (natural D), and the minor seventh Gb. The flat fifth creates a distinct dissonance so it can be used as a substitute for dominant chords only in specific musical contexts. If you keep reading, you will learn more about the music theory that underpins this chord.

 

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Structure of Ab7b5

 

Fingers Position

 

How to play an Ab7b5

Play the root note Ab with your left hand. Then, with your right hand, play the notes Gb (minor 7th), C (major 3rd), and Ebb (diminished 5th).

Ab + Gb, C, Ebb

Omitting the root on your right hand, you can play also one of the three inversions of the chord.

 

Ab7b5 Chord Inversions

 

The Ab7b5 chord has a total of 3 inversions:

 Piano Keyboard Diagrams

 

Ab7b5 Chord Equivalencies

If you take a 7b5 chord, you can find another 7b5 chord that has the same notes in it by either going up three steps from the root note or going down three steps from the root note.

For example, Ab is the root note of Ab7b5 (Ab, C, Ebb, Gb), so if you go up three steps from Ab, you get to Ebb. Therefore, Ebb7b5 has the same notes as Ab7b5.
Similarly, if you go down three steps from Ab, you get to D (D, F#, Ab, C), so D7b5 also has the same notes as Ab7b5.

Ab7b5 = Ebb7b5 = D7b5

The reason why going up three steps or going down three steps leads you to a chord with the same notes is because the interval between the root note and the diminished fifth is called a tritone. This interval is halfway between the octave and divides it into two equal parts. Therefore, going up three steps or going down three steps takes you to the same note that is a tritone away from the starting note.

So, the Ab7b5 chord is equivalent to both Ebb7b5 and D7b5 because they all have the same notes in them, even though they have different names.

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Music Theory and Harmony of Ab7b5

 

Dominant 7b5 chords are often used as transitional chords to add an extra layer of tension to a dominant 7th chord and prepare for the resolution to the tonic. The Ab7b5 chord can substitute or enhance the Ab7 chord, commonly on the V degree in a minor key, but also on the III degree, and occasionally on other degrees as a secondary dominant chord.

Before examining the most common use of this chord, let’s learn how to build it.

 

Building the Ab7b5 Chord: Different Approaches

 

Starting from the Ab Major Scale:

To form a 7b5 chord, you combine the root, the major 3rd, the diminished 5th, and the minor 7th from a major scale.

 

 

 

To create an Ab7b5 chord, apply the formula R, 3, d5, m7 in the following manner:

1. Begin with the Root note, Ab.
2. Select the major 3rd interval, which is C.
3. Add the 5th interval, which is Eb then lower it by half step to get the diminished 5th, Ebb (equivalent to a natural D).
4. Add the minor 7th interval, Gb.

By following this simple formula, you can create a 7b5 chord from any major scale.

 

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by Combining Intervals:

One method to create a 7b5 chord is by combining specific intervals – a major 3rd, a major 2nd, and a major 3rd.

3 + 2 + 3 = 7b5 Chords

For example, to build an Ab7b5 chord:

• we start with the root note Ab.
• We then add a major 3rd interval, which is four half-steps up from the root, to get C.
• Next, we add a major 2nd interval, which is two half-steps (a whole tone) up from C, to get D (Ebb).
• Finally, we add a major 3rd interval, which is four half-steps up from Ebb, to get Gb.

Together, these intervals form the Ab7b5 chord.

 

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How to Use Ab7b5 in a Chord Progression

 

The Ab7b5 can work as a substitute or as a passing chord to an Ab7 that can be found in major and natural minor scales. However, note that it’s a non-diatonic chord due to the presence of the diminished 5th.

These tables show the harmonized major and natural minor scales where you can find an Ab7 or use it in place of other chords.

 

Most common uses of Ab7b5

 

Ab7b5 in Db Major and Db minor

The Ab7b5 chord is commonly used as a dominant chord. In the key of Db major, the Ab7b5 chord can be used as the V7 chord, which leads back to the I chord (Db major).

• Substitute or Passing Chord to the Dominant chord in Db Major.

 

Ab7b5 as Substitute for Abm7

The Ab7 chord derived from the harmonic minor scale is commonly used to replace an Abm7 chord in the key of Db minor. In some cases, the Ab7b5 chord can also be used instead of the Ab7 chord. However, since Db minor is a theoretical key, we will refer to its enharmonic equivalent key, C# minor.

• Substitute or Passing Chord to the Dominant chord in C# minor as G#7b5.

 

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Ab7b5 in a I – III⁷ Progression

The Ab7b5 chord can serve as a substitute for the III chord in a I-III⁷ chord progression that typically features an Ab minor chord. In the chord progression represented by the chords Fb Maj7 and Ab7, the Ab7b5 chord can replace the expected Ab minor chord.

As before we are in a theoretical key (Fb), so we will use its enharmonic equivalent key, E major.

• Substitute or Passing Chord to the Mediant chord in E Major as G#7b5.

 

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Ab7b5 in Bb minor

The Ab7b5 chord in the Bb minor scale could function as a leading tone chord, resolving to the Bb minor chord.

• Substitute or Passing Chord to the Leading Tone chord in Bb minor.

 

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Ab7b5 as Substitute for a Secondary Dominant 7th chord

A secondary dominant is a chord that doesn’t belong to the main key of a song. Instead, it’s used to create a strong pull or tension toward a different chord that does belong to the main key. In Western music, the fifth note of the scale is known for its dominant function, creating tension that typically resolves to the first note of the scale. A secondary dominant serves a similar purpose but directs that tension towards a different chord, briefly taking the music away from the main key.

In the key of Gb major, the Db7 chord serves as the V chord, naturally leading back to Gb Maj7. If you insert an extra chord between Gb Maj7 and Db7, and this new chord strongly leads toward Db7, it transforms into a secondary dominant chord.

For example, introducing an Ab7 chord in this progression creates that pull toward Db7, as Ab7 is the V chord in the key of Db.

| Gb Maj7 | Db7 | Gb Maj7 |

⇒

| Gb Maj7 | Ab7 | Db7 | Gb Maj7 |

To spice up a harmonic progression, you can switch out or combine the standard Ab7 chord with the Ab7b5 chord. This alteration or inclusion can bring in more tension and complexity to the progression.

| Gb Maj7 | Db7 | Gb Maj7 |

⇒

| Gb Maj7 | Ab7/Ab7b5 | Db7 | Gb Maj7 |

 

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Ab7b5 Chord in Major and minor Keys

 

Ab7b5 as Dominant Chord in Db Major

In the key of Db major, the Ab7 chord serves as the dominant chord. However, you can opt to use the Ab7b5 chord instead of or in combination with the Ab7 chord. Here’s how you can approach it:

 

Ab7b5 Chord Progressions as V degree

To get a better understanding of how Ab7b5 works alongside the dominant chord, try playing these chord progressions. Start by playing an Ab7b5 chord for half a measure, followed by an Ab7 chord. This descending tension creates a pleasing sound, especially in the context of the Db Major key.

ii V I

 

I IV V

 

 I V vi IV

 

I IV vi V

 

 I IV ii V iii vi ii V

 

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Ab7b5 as Dominant Chord in Db minor

Check G#7b5 in C# minor

 

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Ab7b5 as III⁷ Degree in Fb Major

Check G#7b5 in E Major

 

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Ab7b5 as Leading Tone Chord in Bb minor

In the key of Bb natural minor, the Ab7 chord is built on the leading tone, which is the seventh note of the scale. This chord can be replaced or modulated by an Ab7b5.

 

Ab7b5 as VII degree – Chord Progressions

 

i iv VII i

 

i VII VI V

 

i III VII VI

 

i iv VII VI

 

i iv VII III

 

Circle Progression

 

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Alternative Ab7b5 Nomenclature

• Ab 7b5
• Lab 7b5
• Ab 7(-5)
• Ab 7/b5
• Ab 7(b5)
• Ab 7b5th
• Ab 7 Flat 5
• Ab Dominant 7th b5
• Ab Dominant Seventh Flat Fifth

 

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Conclusion

The chord progressions and examples presented in this post provide a comprehensive overview of the most common uses of the Ab7b5 chord. It’s important to note, however, that many advanced harmony-related topics could not be included due to space constraints. These topics include chord progressions built on harmonic and melodic scales, modal scales, hidden tonality, secondary dominants and other chord substitutions, non-functional harmony and atonal music, modal interchange and borrowed chords, voice leading and counterpoint, chromatisms, jazz harmony…I mean, music theory is a huge topic!

Although I couldn’t cover all of these topics in my post, I encourage readers to continue exploring these areas in their own study and research. By expanding your knowledge in these advanced areas of music theory, you can gain a deeper understanding of the harmonic possibilities that exist beyond the basics presented here.