Ab7#9 Piano Chord

Piano Diagram of Ab7#9 in Root Position

An Ab7#9 chord is an altered dominant seventh chord that is built upon the key of Ab. This chord consists of the root Ab, the major third C, the perfect fifth Eb, the minor seventh Gb, and the sharp ninth B. The Ab7#9 chord can be used as a substitute for dominant chords only in specific musical contexts. Keep reading to learn more about the music theory that underpins this chord.

 

How to play an Ab7#9

To play an Ab7#9 chord, you can use the following voicing: start by playing the root note Ab with your left hand. Then, with your right hand, play the notes C (major 3rd), Gb (minor 7th), and B (sharp 9th).

Ab + C, Gb, B

This approach will result in a simplified Ab7#9 chord that includes only the essential notes: the root note, major 3rd, minor 7th, and sharp 9th.

 

Ab7#9 Chord Inversions

 

The Ab7#9 chord has a total of 4 inversions:

 Piano Keyboard Diagrams

Chord Inversions on Piano

Having a solid understanding of chord inversions is a crucial element of music theory since it sheds light on how chords are constructed. When it comes to playing chord inversions on a piano, it’s essential to keep in mind that the charts and graphs depicting the order of notes may not always be feasible or even playable.

To achieve the proper chord voicings on a piano, you must spread the chord notes across various octaves and positions on the keyboard. This often entails deviating from the typical shape of the chord’s inversions shown in charts, which may not be the most practical or comfortable way to play the chord.

While chord inversion charts can help understand the structure and sequence of notes in a chord, it’s always a good idea to experiment with different voicings and fingerings to find the most efficient and comfortable way to play the chord, while still preserving its intended harmonic function and sound.

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Music Theory and Harmony of Ab7#9

 

Dominant 7#9 chords are often referred to as the “Hendrix chord” due to their prominent use in songs like “Voodoo Child“, “Foxy Lady“, and “Purple Haze“. If you know these songs, then you can easily recall the distinct sound and mood of the 7#9 chord.

The Ab7#9 chord can replace or enhance the Ab7 chord, typically on the V degree, but also on the III degree, and occasionally on other degrees as a secondary dominant chord. However, it has a distinct funky vibe, so it should be used carefully in the appropriate musical context.

Before delving into the most frequent usage of this chord, let’s first understand how to construct it.

 

Building the Ab7#9 Chord: Different Approaches

 

Starting from the Ab Major Scale:

To form a 7#9 chord, you combine the root, the major 3rd, the 5th, the minor 7th, and the sharp 9th from a major scale.

 

 

 

To create an Ab7#9 chord, apply the formula R, 3, 5, m7, #9 in the following manner:

1. Begin with the Root note, which is Ab.
2. Select the major 3rd interval, which is C, and add it to the chord.
3. Add the 5th interval, which is Eb.
4. Add the minor 7th interval, Gb.
5. Finally, select the 9th (Bb) and add a half tone to get the #9th, B.

By following this simple formula, you can create a 7#9 chord from any major scale.

 

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by Combining Intervals:

One method to create a 7#9 chord is by combining specific intervals – a major 3rd, a minor 3rd, and a perfect 4th.

3 + m3 + m3 + 4 = 7#9 Chords

For example, to build an Ab7#9 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 minor 3rd interval, which is three half-steps up from C, to get Eb.
• Then, we add another minor 3rd so we find the minor 7th Gb and
• lastly, we add a perfect 4th interval, which is five half-steps up from Gb, to get B.

Together, these intervals form the Ab7#9 chord.

 

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How to Use Ab7#9 in a Chord Progression

 

The Ab7#9 can work as a substitute or as a passing chord to an Ab7 that can be found in major and natural minor scales. The 7#9 chord is considered a non-diatonic chord, which means that it contains notes that are not found in either the major or minor scales. Its unique sound is achieved by adding a sharp 9th interval (which is equivalent to a minor 3rd at the higher octave) to the dominant 7th chord, creating a dissonant yet interesting tonal color.

Most common uses of Ab7#9

 

Ab7#9 in Db Major and Db minor

The Ab7#9 chord is commonly used as a dominant chord. In the key of Db major, the Ab7#9 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

 

Ab7#9 as Substitute for Ab min7

The Ab7 chord derived from the harmonic minor scale is commonly used to replace an Ab min7 chord in the key of Db minor. In some cases, the Ab7#9 chord can also be used instead of the Ab7 chord, further enhancing the harmonic tension and leading to the Db min7 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#7#9

 

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Ab7#9 in a I – III7 Progression

The Ab7#9 chord could be used as a substitution for the III degree in an I – III7 chord progression, which traditionally features an Ab minor chord. This chord progression, represented by the chords Fb Maj7 and Ab7, can accommodate the Ab7#9 chord in place of the expected Ab minor chord.

As before, we are in a theoretical key, so it’s more practical to refer to its enharmonic equivalent key E major.

• Substitute or Passing Chord to the Mediant chord in E Major as G#7#9

 

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Ab7#9 in Bb minor

While the Ab7#9 chord can be used in the key of Bb minor, it may not be the most common use of this chord.

• Substitute or Passing Chord to the Leading Tone chord in Bb minor (less common)

 

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Ab7#9 as Substitute for a Secondary Dominant 7th Chord

Ab secondary dominant is a type of chord that is not in the main key of a musical piece but is used to create a strong pull towards another chord that is. In Western music, the fifth scale degree has a strong “dominant” function and creates tension that resolves to the first scale degree chord (I). Ab secondary dominant chord is used to create this same dominant function but towards a different chord, leading to a temporary departure from the main key.

For example, in the key of Gb major, the chord of Db7 is the V chord and leads back to the I chord of Gb Maj7. Adding another chord between Gb Maj7 and Db7 that creates a strong pull towards Db7 creates a secondary dominant chord. In this case, using an Ab7 chord creates a pull towards Db7, as Ab7 is the V chord in the key of Db.

| Gb Maj7 | Db7 |

⇒

| Gb Maj7 | Ab7 | Db7 |

Instead of using a regular Ab7 chord, you can also use the Ab7#9 chord in place of or together with it. This substitution or addition can add more tension and complexity to the progression, leading to a more interesting and dynamic musical result.

| Gb Maj7 | Db7 |

⇒

| Gb Maj7 | Ab7/Ab7#9 | Db7 |

 

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Ab7#9 Chord Function in Major and Minor Keys

 

Ab7#9 as Dominant Chord in Db Major

In the key of Db major, the Ab7 chord would be the dominant chord. The Ab7 chord can be coupled or substituted by an Ab7#9, let’s see how:

 

Ab7#9 Chord Progressions as V degree

Try playing these chord progressions to get an idea of how Ab7#9 functions near the dominant chord. I like to use it followed by an Ab7b9 but feel free to experiment.

ii V I

 

I IV vi V

 

 I IV ii V iii vi ii V

 

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Ab7#9 as Dominant Chord in Db minor

Check G#7#9 in C# minor

 

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Ab7#9 as III7 Degree in Fb Major

Check G#7#9 in E Major

 

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Ab7#9 as Leading Tone Chord in Bb minor

In the key of Bb 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 Ab7#9, although it may not be the most ideal position for this chord. Nonetheless, it can still be a valid option in certain musical contexts.

 

Ab7#9 as VII degree – Chord Progressions

 

i iv VII i

 

i iv VII III

 

Circle Progression

 

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Alternative Ab7#9 Nomenclature

• Ab 7+9
• Ab 7(#9)
• Lab 7#9
• Ab 7#9th
• Ab dom7#9
• Ab Dominant 7th #9
• Ab Dominant Seventh Sharp Ninth

 

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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 Ab7#9 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.