(musTh1) Dominant Seventh Chords

The Basics

Dominant seventh chords, built on the fifth scale degree (with the leading tone raised in minor), are the only diatonic seventh chords to have a Mm7 quality. Since the interval of a seventh is dissonant by definition, chordal sevenths are tendency tones, and seventh chords require special treatment with regard to the approach and resolution of the chordal seventh. 

Approach and Resolution

In discussing the approach and resolution of the chordal seventh, and the dominant seventh chord in particular, it is useful to think about the chord tones of the dominant seventh chord as their respective scale degrees:

• chordal root: scale degree ^5
• third: ^7
• fifth: ^2
• seventh: ^4

The resolution of the chordal seventh is always down by step, from scale degree ^4 to ^3. There are no exceptions. In this regard, it has a stronger tendency to resolve than even a leading tone within a key.

Coupling the resolution of the chordal seventh with a particular approach creates a linear resemblance to four common NHT’s:

• Passing tone (^5 – ^4 – ^3), as part of a I – V7 – I or V – V7 – I progression.
• Neighbor tone (^3 – ^4 – ^3), as part of a I – V7 – I progression.
• Suspension (^4 – ^4 – ^3), as part of a IV – V7 – I, or ii – V7 – I progression.
• Appoggiatura (^2 – ^4 – ^3), as part of a V – V7 – I, or ii – V7 – I progression.

Root Position Resolution of V7 to I

Resolution of the V7 chord requires handling the two tendency tones, the leading tone and the chordal seventh. If the leading tone is in the upper voice, it must resolve up by step. If both the V7 and I chords are in root position, then either the V7 or the I chord must be incomplete. Incomplete I chords can only appear at cadences.

Complete V7 to incomplete I involves the following scale degree movements (resolution):

• ^4 – ^3
• ^2 – ^1
• ^7 (in soprano) – ^1
• ^5 (root in bass) – ^1 (root in bass)

An incomplete V7 will have the root doubled and the fifth omitted. An incomplete V7 to complete I will involve:

• ^4 – ^3
• ^7 (in soprano) – ^1
• ^5 (not bass) – ^5
• ^5 (root in bass) – ^1

If the leading tone is not in the soprano, its natural tendency can be frustrated. In this case ^7 jumps down to ^5. Do not insert a passing tone between ^7 and ^5. It calls intention to what is a resolution fake out. The resolution of the chord will look like:

• ^4 – ^3
• ^2 – ^1
• ^7 – ^5 (frustrated leading tone resolution)
• ^5 (root in bass) – ^1 (root in bass)

Notice that in addition to the root movement of ^5 – ^1, and the chordal seventh resolution of ^4 – ^3, that the chordal fifth (if present) will always move ^2 – ^1.