Bb7#5 Piano Chord

Piano Diagram of Bb7#5 in Root Position

A Bb7#5 chord is an altered dominant seventh chord that is built upon the key of Bb. This chord consists of the root note Bb, the major third D, the augmented fifth F# and the minor seventh Ab. However, due to the dissonance created by the augmented triad, the Bb7#5 chord can be used as a substitute for dominant chords only in specific musical contexts. Another common use of this chord is as part of a modulation to or from a Bb7 chord. If you keep reading, you will learn more about the music theory that underpins this chord.

 

---

Structure of Bb7#5

 

Fingers Position

How to play a Bb7#5

To play a Bb7#5 chord, you can use the following voicing: begin by playing the root note Bb with your left hand. Then, with your right hand, play the notes Ab (minor 7th), D (major 3rd), and F# (sharp 5th).

Bb + Ab, D, F#

This will result in a voicing of Bb7#5 that includes all notes: the root note, major 3rd, minor 7th, and sharp 5th.

 

Bb7#5 Chord Inversions

 

The Bb7#5 chord has a total of 3 inversions:

 Piano Keyboard Diagrams

Chord Inversions on Piano

A solid grasp of chord inversions is essential in music theory as it provides insights into how chords are built. When playing chord inversions on a piano, it’s crucial to realize that the charts depicting the note order may not always be practical or playable.

To achieve the correct chord voicings on a piano, you need to distribute the chord notes across different octaves and positions on the keyboard. This often involves deviating from the standard shape of the chord’s inversions presented in charts, which may not be the most practical or comfortable way to play the chord.

While chord inversion charts are useful for understanding the structure and sequence of notes in a chord, it’s advisable to experiment with different voicings and fingerings to discover the most efficient and comfortable way to play the chord, while still maintaining its intended harmonic function and sound.

---

Music Theory and Harmony of Bb7#5

 

Dominant 7#5 chords are often used as a transitional chord to add an extra layer of tension to a dominant 7th chord and prepare for the resolution to the tonic. The Bb7#5 chord can substitute or enhance the Bb7 chord, commonly on the V degree, 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 Bb7#5 Chord: Different Approaches

 

Starting from the Bb Major Scale:

To form a Bb7#5 chord, you combine the root (Bb), the major 3rd (D), the augmented 5th (F#), and the minor 7th (Ab) from the Bb scale.

 

 

 

To create a Bb7#5 chord, apply the formula R, 3, #5, m7 in the following manner:

1. Begin with the Root note, Bb.
2. Select the major 3rd interval, which is D.
3. Add the 5th interval, which is F then raise it by half step: F#.
4. Add the minor 7th interval, Ab.

By following this simple formula, you can create a 7#5 chord from any major scale.

 

---

by Combining Intervals:

One method to create a 7#5 chord is by combining specific intervals – a major 3rd, a major 3rd, and a 2nd.

3 + 3 + 2 = 7#5 Chords

For example, to build a Bb7#5 chord:

• we start with the root note Bb.
• We then add a major 3rd interval, which is four half-steps up from the root, to get D.
• Next, we add another major 3rd interval, which is again four half-steps up from D, to get F#.
• Finally, we add a 2nd interval, which is two half-steps up from F#, to get Ab.

Together, these intervals form the Bb7#5 chord.

 

---

How to Use Bb7#5 in a Chord Progression

 

The Bb7#5 can work as a substitute or as a passing chord to a Bb7 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 augmented 5th.

These tables show the harmonized major and natural minor scales where you can find a Bb7 or use it in place of other chords.

Most common uses of Bb7#5

Bb7#5 in Eb Major and Eb minor

The Bb7#5 chord is a popular choice for creating tension in music, often functioning as a dominant chord. In the context of the key of Eb major, you can use Bb7#5 as the V7 chord, setting the stage for a resolution back to the I chord (Eb major).

• Substitute or Passing Chord to the Dominant chord in Eb Major

 

Bb7#5 as Substitute for Bb min7

The Bb7 chord, taken from the harmonic minor scale, is frequently chosen to substitute for a Bb min7 chord in the key of Eb minor. In certain situations, you can also opt for the Bb7#5 chord instead of the Bb7 chord, intensifying the harmonic tension and guiding the progression towards the Eb min7 chord.

• Substitute or Passing Chord to the Dominant chord in Eb minor

 

---

Bb7#5 in a I – III7 Progression

The Bb7#5 chord is frequently employed as a substitute for the III degree in a I – III7 chord progression. This progression typically involves a Bb minor chord, but when using the chords Gb Maj7 (I) and Bb7 (III7), you can introduce the Bb7#5 chord instead of the usual Bb minor chord.

The Bb7#5 chord contributes a distinctively dissonant augmented triad, adding a unique flavor to the progression.

• Substitute or Passing Chord to the Mediant chord in Gb Major

 

---

Bb7#5 in C minor

Although the Bb7#5 chord can find a place in the key of C minor, it might not be as commonly used in this context. In fact, its resolution to C minor may not be as strong as its resolution to Eb major or Eb minor.

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

 

---

Bb7#5 as Substitute for a Secondary Dominant 7th chord

A secondary dominant is a chord that doesn’t belong to the main key of a musical piece but is used to strongly lead to another chord that does. In Western music, the fifth note of the scale has a powerful “dominant” role, creating tension that naturally resolves to the first note of the scale (I). A secondary dominant chord serves the same purpose but directs this dominant function to a different chord, causing a temporary shift away from the main key.

For instance, in the key of Ab major, the Eb7 chord serves as the V chord, leading back to the I chord of Ab Maj7. Introducing an additional chord between Ab Maj7 and Eb7 that strongly gravitates towards Eb7 results in a secondary dominant chord. In this scenario, including a Bb7 chord generates a pull towards Eb7, as Bb7 functions as the V chord in the key of Eb.

| Ab Maj7 | Eb7 |

⇒

| Ab Maj7 | Bb7 | Eb7 |

Instead of using a standard Bb7 chord, you can opt for the Bb7#5 chord in its place or in combination with it. This substitution or addition can add more tension and complexity to the progression, leading to a more interesting and dynamic musical result.

| Ab Maj7 | Eb7 |

⇒

| Ab Maj7 | Bb7/Bb7#5 | Eb7 |

 

---

Bb7#5 Chord Function in Major and Minor Keys

 

Bb7#5 as Dominant Chord in Eb Major

In the key of Eb major, the Bb7 chord would be the dominant chord. The Bb7 chord can be coupled or substituted by a Bb7#5, let’s see how:

 

Bb7#5 Chord Progressions as V degree

Try playing these chord progressions to get an idea of how Bb7#5 functions near the dominant chord. Begin by playing a Bb7 for half a measure, followed by a Bb7#5. This will create an ascending tension that sounds particularly pleasing in the key of Eb Major.

ii V I

 

I IV V

 

 I V vi IV

 

I IV vi V

 

 I IV ii V iii vi ii V

 

---

Bb7#5 as Dominant Chord in Eb minor

The Bb7 chord can also be located on the V degree of the Eb harmonic and melodic minor scales. It’s frequently employed in conjunction with chords based on the natural minor scale or as a substitute for the Bb min7 chord found in the natural minor scale. In certain contexts, a Bb7#5 can be used instead of a Bb7 in this role, providing a different harmonic flavor.

 

Bb7#5 as V degree on Minor Scale – Chord Progressions

Try playing these chord progressions to get an idea of how Bb7#5 functions as the subdominant (V degree) in the key of Eb minor. I recommend playing a Bb7 chord within the same measure as the Bb7#5 chord, as it adds a sense of harmonic movement to the progression.

 

ii V i

 

i iv V

 

i iv VI V

 

i VI V iv

 

Circle Progression

 

---

Bb7#5 as III7 Degree in Gb Major

This is a very common substitution of dominant chords in place of minor chords. In the case of Bb7, we are in Gb major since the minor chord we are going to substitute is on the iii degree of the scale:

 

Bb7#5 as III7 degree – Chord Progressions

Try playing these chord progressions to get an idea of how Bb7#5 functions in this position. To understand why this substitution is possible, I suggest checking out some of the posts related to dominant 7th chords. There are different interpretations of this substitution, so it can be helpful to explore them to fully understand its potential use.

 

I III⁷ vi

 

I III⁷ VI⁷ ii

 

I III⁷ IV VI⁷ ii V iii/biii^ø ii/V

---

Bb7#5 as Leading Tone Chord in C minor

In the key of C minor, the Bb7 chord is constructed on the leading tone, which is the seventh note of the scale. This chord can be substituted or changed to a Bb7#5, although it might not be the most optimal position for this chord. Nevertheless, it remains a valid choice in specific musical situations.

 

Bb7#5 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

 

---

Alternative Bb7#5 Nomenclature

• Bb 7+5
• Bb 7(#5)
• Bb aug7
• Sib  7#5
• Bb 7#5th
• Bb 7aug5
• Bb Dominant 7th #5
• Bb Dominant Seventh Sharp Fifth

 

---

Conclusion

The chord progressions and examples presented in this post provide a comprehensive overview of the most common uses of the Bb7#5 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.