C7#5 Piano Chord

Piano Diagram of C7#5 in Root Position

The C7#5 chord is an altered dominant seventh chord built upon the root of C. This chord consists of the root note C, the major third E, the augmented fifth G#, and the minor seventh Bb. Due to the intense dissonance created by its internal augmented triad, the C7#5 chord is one of the most powerful harmonic engines in modern music. The sharp fifth (G#) acts as a fierce leading tone that creates strong upward tension, demanding a resolution to the target chord. It frequently appears in jazz, neo-soul, gospel, and classical music to pull the listener aggressively forward. If you keep reading, you will learn the exact music theory that underpins this chord and explore the advanced chord progressions that utilize it.

 

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Structure of C7#5

 

Fingers Position

 

How to play the C7#5 chord

To play the C7#5 chord, you can use the following voicing: begin by playing the root note C with your left hand. Then, with your right hand, play the notes Bb (minor 7th), E (major 3rd), and G# (sharp 5th).

C + Bb, E, G#

This open voicing prevents the chord from sounding too muddy, clearly articulating the essential dissonance between the minor 7th and the sharp 5th.

 

C7#5 Chord Inversions

 

The C7#5 chord has a total of 3 inversions:

Piano Keyboard Diagrams

Chord Inversions on Piano

Understanding chord inversions is essential in music theory as it provides insights into how harmonies flow into one another. When playing altered chords like the C7#5 on a piano, it is crucial to realize that the fundamental block structures depicting the note order may not always be practically playable or musically pleasing.

To achieve professional-sounding voicings, you must distribute the notes across different octaves. Playing a sharp fifth directly next to a minor seventh in the lower register can sound extremely muddy. While basic inversion charts are mathematically correct, you should experiment with wide, two-handed voicings to discover the most efficient way to play the chord while maintaining its intended harmonic function.

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Music Theory and Harmony of C7#5

 

Altered dominant chords like the C7#5 are frequently used as transitional devices to add an extra layer of tension to a standard dominant 7th chord, preparing the ear for a powerful resolution to the target chord. The C7#5 chord seamlessly substitutes the regular C7 chord, commonly appearing on the V degree, but also functioning on the III degree or serving as a secondary dominant to briefly shift the tonality.

Before examining the most practical and stylistic uses of this chord, let’s learn how to build it.

 

Building the C7#5 Chord: Different Approaches

 

Starting from the C Major Scale:

To form the C7#5 chord, you combine the root note C, the major 3rd E, the augmented 5th G#, and the minor 7th Bb from the C scale.

 

 

To create the C7#5 chord from a scale, apply the formula R, 3, #5, m7 in the following manner:

1. Begin with the root note, C.
2. Select the major 3rd interval, which is E.
3. Find the perfect 5th interval (G), then raise it by a half-step to get the augmented 5th: G#.
4. Finally, add the minor 7th interval, which is Bb.

By following this formula, you can construct a 7#5 chord starting from any root note.

 

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by Combining Intervals:

Another practical method to create the 7#5 chord is by stacking specific intervals on top of each other.

Major 3rd + Major 3rd + Major 2nd = 7#5 Chord

For example, to build the C7#5 chord:

• Start with the root note C.
• Add a major 3rd interval (four half-steps up) to land on E.
• Stack another major 3rd interval on top of the E (four half-steps up) to get G#.
• Finally, add a major 2nd interval (two half-steps up) from G# to get Bb.

These stacked intervals perfectly map out the C7#5 chord.

 

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How to Use C7#5 in a Chord Progression

 

The C7#5 is an incredibly versatile tool for reharmonization. Whenever you have a standard C7 chord resolving to an F Major or F minor chord, the C7#5 can be swapped in to drastically improve the voice leading. Because of the sharp fifth (G#), the chord is non-diatonic to standard major or natural minor scales, acting as a borrowed chromatic color that creates intense forward motion.

Let’s break down its most effective and musically compelling uses across different key signatures, massively expanding on standard jazz and gospel cadences.

 

Most common uses of C7#5

C7#5 as the Dominant (V) in F Major

In the key of F Major, the standard dominant chord is C7. By substituting it with C7#5, the altered note (G#) acts as a sharp passing tone that pulls chromatically upward, landing perfectly on the major third (A) of the target F Maj7 chord.

• Substitute for the V chord to create an ascending chromatic resolution.

 

ii V I

This is the absolute standard jazz cadence. The sharp fifth (G#) of the C7#5 resolves a half-step up into the A note of the F Maj7, creating an incredibly satisfying and smooth release of tension.

 

I vi ii V

In this classic turnaround, the intense dissonance of the C7#5 acts as a massive slingshot at the end of the phrase, forcing the progression to aggressively loop back to the stable I chord.

 

I V/ii ii V

By substituting the diatonic vi chord with a secondary dominant (D7#5), we create a chain of heavily altered falling fifths. The final dominant is the C7#5, perfectly preparing the listener for the definitive resolution home.

 

Line Cliché: V V V V I

Instead of moving the root of the chord, the fifth shifts chromatically up and down (G to G# to A to G#) over a static bass line, generating a beautiful internal melody before resolving.

 

Deceptive Cadence (Half-Step Up): ii V bVI

Instead of resolving to the tonic, the V chord slips up a half-step to the flat submediant. The G# functions as the fifth of the Db chord (Ab), modulating with elegance while still starting from the dominant of F.

 

Deceptive Cadence (Minor Third Down): V III

Another surprise from the dominant seat: instead of landing on F, the C7#5 leaps down to the mediant. The augmented fifth acts as a leading tone that lands smoothly on the A root.

 

Chain of Dominants: V/V/V V/V V I

A pure chain of dominants falling in fifths toward home. Each chord is the dominant of the next, and altering only the final link as a C7#5 saves the sharpest tension for the last moment, its raised fifth (G#) climbing to the A of F Maj7.

 

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C7#5 as the Dominant (V) in F minor

When resolving to a minor chord, the C7#5 is arguably at its most powerful. The augmented fifth (G#) is enharmonically equivalent to Ab—which is exactly the minor third of the target F min7 chord. This means the altered note doesn’t even need to move; it acts as a common tone, gluing the two chords together.

• Substitute for the V chord to seamlessly lock into the minor tonic.

 

iiø V i

The dark, diminished color of the ii chord perfectly prepares the ear for the C7#5, which then effortlessly resolves into the melancholy F min7 using the G# as a stable anchor.

 

Minor Blues Turnaround: i iiø V i

In the final cadence of a minor blues, swapping the standard dominant with the C7#5 highlights the dramatic, tense flavor of the harmonic minor scale right before returning to the top of the form.

 

Complex Resolution: ii V i

Resolving to a dense minor 6/9 chord creates a beautiful chiaroscuro effect typical of modal jazz, with the augmented fifth of the dominant chord sliding flawlessly into the minor third of the resolution.

 

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C7#5 as Secondary Dominant (I7) in C Major

This is an incredibly fun approach often found in blues and gospel. In the key of C Major, you alter the home chord (C Maj7) into a dominant structure (C7#5). Because C is the V of F, this treats the IV chord (F Maj7) as the new temporary tonal center.

• Substitute for the Tonic chord to act as a Secondary Dominant (V/IV).

 

I I⁷ IV iv

A highly emotional sequence. We start securely on the major tonic, but morph it into the biting C7#5. The G# pushes aggressively into the A of the F Maj7, which is then beautifully darkened by a minor plagal cadence.

 

Blues Quick Change: I I⁷ IV

Used rhythmically in a blues progression, swapping the standard dominant with the C7#5 on the last beat before the change creates a fierce leading tone pulling toward the subdominant.

 

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C7#5 as Secondary Dominant (VI7) in Eb Major

Substituting the diatonic minor vi chord with a dominant structure is a fundamental jazz reharmonization. In Eb Major, changing the C min7 to a C7#5 turns it into a secondary dominant targeting the ii degree.

• Substitute for the Submediant chord to target the ii degree.

 

Diminished Substitution: I VI⁷ ii

Using the C7#5 over the third in the bass (E) offers a modern, bright alternative to the traditional passing diminished chord (#Idim7), while sharing an almost identical ascending bass line.

 

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C7#5 as a Tritone Substitution (subV) in B Major / B minor

A tritone substitution occurs when you replace a dominant 7th chord with another dominant 7th located exactly three whole steps (a tritone) away. In the key of B, the standard V chord is F#7. The tritone substitution for F#7 is C7.

By using the altered C7#5 instead of a plain C7, the voice leading becomes incredibly rich, as the chord slides chromatically downward into the B tonic.

• Substitute for the Dominant chord as a Tritone Substitution (subV) to target the tonic B.

 

ii subV I

An incredibly slick jazz resolution. The bass line steps down chromatically, while the sharp fifth of the C7#5 creates a suspenseful harmony that glides perfectly onto the B Major chord.

 

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Advanced Reharmonizations with C7#5

The C7#5 chord excels in situations meant to surprise the listener. Whether moving in unexpected directions or participating in symmetrical cycles, its tense nature makes it a favorite among advanced players.

Coltrane Cycle: I bIII⁷ bVI VII⁷ III V⁷ I

Descending by major thirds, the C7#5 and its peers soften the brutal tonal shifts of Coltrane changes by utilizing the symmetry of their augmented triads to smooth out the voice leading.

Backdoor Progression: iv bVII⁷ I

Acting as the bVII7 chord, the C7#5 creates a formidable chromatic grip where the sharp fifth (G#) climbs gracefully to A, the fifth of the D Maj7.

 

Gospel Walk-Up: I III⁷ IV

A staple of Rhythm & Blues and Gospel playing. The C7#5 acts as a heavily altered secondary dominant to the IV chord, violently pushing the ear forward while the upper voices expand.

 

Constant Structure Pedal: V/II bVII/II V/II bIII/II

A brilliant funk and fusion trick. By moving the exact 7#5 block voicing parallel over a static bass note, the progression generates intensely modern poly-chordal tension without changing its aggressive intention.

 

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Alternative C7#5 Nomenclature

• C 7+5
• C 7(#5)
• C aug7
• Do 7#5
• C 7#5th
• C 7aug5
• C Dominant 7th #5
• C Dominant Seventh Sharp Fifth

 

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Conclusion

The chord progressions and structural concepts presented in this post provide a vast and practical toolkit for deploying the C7#5 chord on the piano. By exploring its chromatic functions—whether the sharp fifth acts as a common tone, an ascending leading tone, or part of a tritone substitution—you unlock its true harmonic power.

While this guide covers the most effective scenarios across major, minor, gospel, and jazz contexts, modern harmony offers countless other pathways. Once you master inserting altered dominants into standard ii-V-I cadences and secondary dominant slots, continue expanding your vocabulary. Keep experimenting with the internal voice leading, trust your ears, and enjoy the rich tensions this chord brings to your arrangements.