C7 Piano Chord

Piano Diagram of C7 in Root Position

A C7 chord is a dominant 7th chord built upon the key of C. It’s made by the root note C, the major 3rd E, the perfect 5th G, and the minor 7th Bb. The C7 chord can be found on the fifth degree of several scales. Keep reading to understand the music theory behind this chord.

 

 

C7 Chord Inversions

 

The C7 chord has a total of 3 inversions:

 Piano Keyboard Diagrams

---

Music Theory and Harmony of C7

 

What are Dominant Seventh Chords?

A dominant 7th chord is a four-note chord that consists of a major triad with a minor 7th added. Dominant 7th chords are important chords in music theory, as they add a sense of tension and instability that can lead to the resolution of the chord. They have a strong pull toward the tonic, making them common in cadences and progressions.

Let’s see how to build this kind of chord:

 

---

Building the C7 Chord: Different Approaches

 

Starting from the C Major Scale:

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

 

 

To create a C7 chord, 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, and add it to the chord.
3. Add the 5th interval, G.
4. Add the minor 7th interval, which is Bb.

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

 

---

by Combining Intervals:

One method to create a dominant 7th chord is by combining specific intervals – a major 3rd, a minor 3rd, and again a minor 3rd.

3 + m3 + m3 = Dominant 7th Chords

For example, to create a C7 chord, we start with the root note C.

We then add a major 3rd interval, which is four half-steps up from the root, to get E.

Next, we add a minor 3rd interval, which is three half-steps up from E, to get G.

Finally, we add another minor 3rd interval, which is three half-steps up from G, to get Bb. Together, these intervals form the C7 chord.

 

---

Characteristics of the C7 Chord

Dominant 7th chords are often used as transitional chords to add tension and prepare for the resolution to the tonic. They have a distinct sound that is often described as “bluesy” or “jazzy”. From a theoretical point of view, it is an unstable chord because it contains a tritone, an interval of three whole tones between the 3rd and 7th degree.

The ii-V-I Progression

In the key of F major, this progression would involve playing the chords G minor (ii), C7 (V), and F major (I) in sequence.

When played as G minor, C major, and F major, the progression may sound complete but lacks the tension and resolution provided by the C7 chord. The minor 7th interval adds a layer of tension to the progression, creating a sense of expectation for the resolution to the F major chord.

 

C7 Chords and Key Tonality

Another feature of 7th chords is that they are typically built on the fifth degree of the major scale. As a result, when we play a dominant 7th chord in a piece of music, it can suggest the tonality (or key) because the chord often resolves to the I degree of the chord progression.

For example, if you come across a C7 chord in a piece of music, it suggests that you are likely playing in the key of F (major or minor since the C7 is also present on the F harmonic minor scale) or its relative D minor key since C is the fifth degree of the F major scale and the 7th degree of the D minor scale.

However, it’s important to note that a C7 chord could be also used on other degrees or in a non-diatonic way, so it’s essential to consider the broader harmonic context before determining the key of the piece.

 

---

How to Use C7 in a Chord Progression

The C7 chord is a versatile chord that can be used to add tension, create movement, and establish resolution in your chord progressions. It is commonly employed in all genres, from jazz, rock, and pop to folk and traditional music.

The C7 chord carries a dominant function, which means it naturally resolves to a chord that represents a point of stability or home within a musical key. Here are some of the most common uses of the C7 chord:

---

Most common uses of C7

These tables show the harmonized major and natural minor scales where you can find a C7 or use it in place of other chords.

C7 on Major and minor Scales

• Dominant chord in F Major

 

• Leading Tone chord in D minor

 

---

C7 as Substitute for Cm7

In this case, the C7 chord is derived from the harmonic minor scale and is commonly used as a substitute for a Cm7 chord on the V degree.

• Dominant chord in F minor

 

---

C7 in Blues Progressions

• Tonic chord in C Major
• Subdominant chord in G Major
• Dominant chord in F Major

 

---

C7 in a I – III⁷ Progression

In a I – III⁷ chord progression, (Ab Maj7 | C7), the III degree, which should be a C minor chord, is often played as a C7 chord. There are multiple explanations for this substitution, all of which are correct and provide different interpretations:

1. Dominant Chord Substitution: In the key of Ab Major, the V degree chord is typically represented by an Eb7 chord. However, it is possible to use a diminished 7th chord as a substitute for the dominant 7th just by raising the root of the 7th chord by a half-step. In the case of the Eb7 chord, it can be replaced by an E diminished 7th chord (Eb, G, Bb, Db becomes E, G, Bb, Db). By lowering just one note of the E diminished 7th chord, E, G, Bb, Db becomes E, G, Bb, C, which is an inversion of the C7 chord.

Eb, G, Bb, Db ⇒

E, G, Bb, Db ⇒

E, G, Bb, C

2. Prepared Modulation I – III⁷ – vi: In Ab Major, the relative minor key is F minor. Therefore, introducing the V degree (C7) of the relative minor key (Fm) as a modulation that resolves on the vi degree (Fm) is a valid explanation for this substitution.

| Ab Maj7 | F min7 |  ⇒ 

| Ab Maj7 | C7 | F min7 |

3. Secondary Dominant: In Ab Major, the V of the VI degree (Fm) is C.

 

---

C7 in a Tritone Substitution

The term “Tritone Substitution” is a musical concept where a dominant 7th chord is replaced by another dominant 7th chord that is a tritone away. This means that instead of using the original dominant chord, a musician substitutes it with a chord that is located six semitones above or below the original.

In the context of a ii-V-I chord progression, which is a common jazz chord progression, the tritone substitution can be represented as “ii-SubV7-I”. This means that the ii chord is followed by a substitute dominant 7th chord, which then resolves to the I chord.

This type of substitution works because shares the third and 7th notes. This creates a chromatic movement that adds interest and tension, leading toward the tonic chord. The tritone substitution works because the substitute dominant chord shares the same 3rd and 7th notes as the original dominant chord but in reverse order.

For example, if the original dominant chord is F#7 (F#, A#, C#, E), the substitute dominant chord would be C7 (C, E, G, Bb), as both chords share the notes Bb (A#) and E, which are the 3rd and 7th notes.

It’s important to note that C7 is a non-diatonic chord in the key of B. This means that while it may sound good in certain musical contexts, it’s important to be careful and not clash with the melody or other harmonic elements of the composition.

 

---

C7 as Secondary Dominant chord

A 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 toward 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). A secondary dominant chord is used to create this same dominant function but toward a different chord, leading to a temporary departure from the main key.

| Bb Maj7 | F7 |  ⇒ 

| Bb Maj7 | C7 | F7 |

Let’s take the key of Bb major as an example. In this key, the F7 chord acts as the dominant V chord, leading back to the Bb Maj7 chord, which is our tonic I chord. Now, if we want to add an extra chord between Bb Maj7 and F7 that creates a strong pull toward F7, we introduce a secondary dominant chord. To achieve this, we can use a C7 chord because, in the key of F, C7 serves as the dominant V chord. This way, the C7 chord enhances the tension and directs our ears toward the resolution on F7.

 

---

C7 Chord Function in Major and Minor Keys

 

Understanding Scale Degrees

• Starting with the first degree of the scale, we have the Tonic chord. This chord serves as the foundation of the scale, providing a stable tonal center for the music. It’s like the “home base” of the music, and all melodies and harmonies are anchored to this chord.
• Moving on to the second degree, we have the Supertonic. This degree acts as a transitional note between the tonic and other notes in the scale, creating a sense of movement and flow in the melody or harmony.
• The third degree is the Mediant, which is located halfway between the tonic and dominant notes. This degree helps to establish whether the scale is major or minor and plays a critical role in determining the mood and emotional impact of the music.
• The fourth degree is the Subdominant, which complements the dominant and adds tension and resolution to the music. It creates a push-pull effect that keeps the listener engaged and interested.
• The fifth degree is the Dominant, which generates tension and a sense of expectation. It often acts as the climax of a musical phrase or section and is resolved by returning to the tonic.
• The sixth degree is the Submediant, which provides a sense of stability and restfulness to the music. It’s often used as a transition between the dominant and tonic, creating a feeling of calm and relaxation.
• Finally, we have the 7th degree, the Leading tone. This degree produces a strong sense of tension and a desire to resolve to the tonic. It’s often used to create a sense of resolution and completion in the melody or harmony.

Understanding the scale degrees is essential for creating chords and understanding how they relate harmonically to one another. By knowing the function of each degree, we can create more interesting and effective harmonies in our music.

 

---

C7 as Dominant Chord in F Major

In the key of F major, the C7 chord would be the dominant chord. The C7 chord has a strong pull to resolve to the tonic chord F Maj7.

 

C7 Chord Progressions as V degree

Try playing these chord progressions to get an idea of how C7 functions as the dominant chord.

ii V I

 

I IV V

 

 I V vi IV

 

I IV vi V

 

I IV vii iii vi ii V I

 

---

C7 as the Leading Tone Chord in D minor

In the D minor scale, C7 is the chord built on the leading tone, which is the 7th note of the scale. This chord creates a strong pull toward the tonic chord, D min7.

 

C7 as VII degree – Chord Progressions

These chord progressions can help you understand how C7 serves as the leading tone:

 

i iv VII i

 

i VII VI V

 

i III VII VI

 

i iv VII III

 

Circle Progression

 

---

C7 as Dominant chord in F minor

C7 can be found also on the F harmonic minor scale, as it is the V chord in that scale. It’s very common to use this chord in combination with chords built on the natural minor scale or to substitute it for the C min7 chord that is present in the natural minor scale.

 

C7 as V degree on Minor Scale – Chord Progressions

Try playing these chord progressions to get an idea of how C7 functions as the subdominant (V degree) in the F minor key.

 

ii V⁷ i

 

i iv V⁷

 

i iv VI V⁷

 

i V⁷ VI VII

 

i VI V⁷ iv

 

Circle Progression

 

---

C7 as Tonic Chord in a Blues Progression in C

In the key of C major, the first chord is a C Maj7 but in some contexts, it can be substituted with a C7.

 

One such context is in the blues genre, where the use of dominant 7th chords as tonics is common.

Blues music draws its foundation from the Mixolydian scale, which is a variation of the major scale. The Mixolydian scale is characterized by having a flattened 7th note compared to the major scale.

When we consider the key of C major, the 7th note is B. However, in the Mixolydian scale used in blues music, the 7th note is flattened, which means it is lowered by a half step. Consequently, the B note in the C major scale becomes a Bb in the Mixolydian scale.

This alteration of the 7th note from B to Bb in the Mixolydian scale is significant because it creates a minor 7th interval. In other words, when we build a dominant 7th chord on the tonic C using the Mixolydian scale, we get a C7 chord.

It is this altered 7th note and the resulting minor 7th interval that contributes to the bluesy and soulful atmosphere associated with the genre.

In the context of blues music, a C7 chord can serve as:

1. the tonic chord (I) in the key of C,
2. the subdominant (IV) in the key of G,
3. the dominant chord (V) in the key of F.

This is because blues music uses a specific chord progression known as the 12-bar blues, which consists of three chords played over 12 bars.

 

C7 as I degree in a Blues Progression in C

In the key of C, the 12-bar blues progression would typically be C7 (I), F7 (IV), and G7 (V) chords, with the C7 chord serving as the tonic and the other two chords as the subdominant and dominant, respectively.

 

Blues Chord Progression in C

 

Blues Chord Progression in C – Variation

 

---

C7 as Subdominant Chord in a Blues Progression in G

In a blues progression in the key of G, C7 can serve as a subdominant chord. In this context, C7 is typically played in the fifth, sixth, and tenth measure of a twelve-bar blues progression.

 

C7 as IV degree in a Blues Progression in G

 

Blues Chord Progression in G

 

Blues Chord Progression in G – Variation

 

---

C7 as Dominant Chord in a Blues Progression in F

In the key of F, when playing a blues progression, C7 takes on the role of the dominant chord. Specifically, in a twelve-bar blues progression, C7 is commonly played in the 9th and 12th measures.

 

C7 as IV degree in a Blues Progression in F

 

Blues Chord Progression in F

 

Blues Chord Progression in G – Variation

 

---

C7 as III⁷ Degree in Ab Major

This is a very common substitution of dominant chords in place of minor chords. In the case of C7, we are in Ab major since the minor chord we are going to substitute is on the iii degree of the scale:

 

C7 as III⁷ degree – Chord Progressions

Try playing these chord progressions to get an idea of how C7 functions on the 3rd degree in the Ab Major key.

 

I III⁷ vi

 

I III⁷ VI⁷ ii

 

I III⁷ IV VI⁷ ii V iii/biii^ø ii/V

---

Alternative C7 Nomenclature

• C7
• Do7
• C7th
• C dom7
• C dominant 7th

 

---

Conclusion

The chord progressions and examples presented in this post provide a comprehensive overview of the most common uses of the C7 chord. It’s important to note, however, that there are many advanced harmony-related topics that 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.