Which other chords are considered equivalent or function like a V7?

Question

A dominant seventh chord as the fifth degree of a key (notated V7) is often used to build a cadence back to the tonic.

With that function in mind, I've seen people refer to other chords as "it functions as a V7", but without the chord itself being a V7. One example I know of is applying tritone substitution to the V7 chord, which changes the chord but not its function.

When composing, which other chords should I have in mind that function like a V7 but are no the V7 chord? If there are too many possibilities, which are the most common V7 substitutions in western music (pop, rock, jazz, classical)?

Answer 1

• Any chord built from a dominant triad can function like a V7. (Ex. 1 for an incomplete list)

• Diminished chords, both diminished triads and sevenths, can act as dominants with the root truncated. (Ex. 2) Semi-diminished sevenths (Tristan chords) are generally used as pre-dominants, but can stand in for V M9 with the root truncated. (Ex. 2c)

• Augmented sixth chords - Italian (Ex. 3a), French (Ex. 3b) and German (Ex. 3c) - normally function as pre-dominants, but can function as dominants: they tend to combine a Phrygian cadence with a dominant or dominant-like progression in one or more of the upper voices. (The German sixth really prefers to act as a pre-dominant, though - in Classical music it generally resolves through a ⁶₄ chord, as here, to avoid rather bald parallel fifths.)

Your "tritone substitution" is an augmented sixth, by the way: take a look at the makeup of the German sixth. This isn't so much a tritone substitution: it's a modal substitution that has been given mixed function by sharping one of the notes into a leading tone (the Italian sixth) and, in this case, adding another tendency tone. It's an artifact of voice leading that arose from the old Phrygian final cadence (♭vii⁶-I).

If augmented sixth chords are mostly used now as pre-dominants, it's because the Phrygian cadence fit very neatly into the minor mode as iv⁶-V. However, they can still be used for cadences to the tonic, and they can be even dropped into a major mode context. I've done so here in m.32.

• Finally, there is V7^♭5 (Ex. 4) and its derivatives. I've shown the basic chord and followed it by its first and second inversions. Note the latter (Ex. 3b)!

There are undoubtedly variants I've missed. In general a chord can be made to function as a dominant harmony if it possesses the ascending leading tone and (usually) the descending leading tone and/or the fifth of the tonic. Not infrequently, in major modes, major-like modes and Picardy thirds, you'll also have 4-3 (fa-mi) in one of the voices.

Answer 2

One chord which will easily substitute is vii; for the key of C major, this will be the diminished triad B-D-F. V7 would be G7, i.e. G-B-D-F, so the only difference is that V7 has the dominant in the bass whereas vii is lacking this note.

There is also the 'deceptive cadence', which in C would be C#major (or C#7). This works better in minor keys.

Answer 3

A couple I use instead of V (or V7) - in C - B D F Ab and C D F Ab. The first is Bo, the second Fm6. Bo resolves the B to C and the Ab to G, whereas the Fm6 seems to suspend things before resolving to Cmaj. There's also G+, which is different from G7, with its augmented 5th, leading up to the major 3 of the tonic. Another that works in certain places is B D# F# - Bmaj. Don't know the name of this cadence, but it certainly gets the listener's attention! And, rather like a tritone sub., resolution is only a semitone away.G#7 works in similar vein, with 3 of its notes needing to move that one semitone - although it can seem to herald a key change. I think Mahler used it occasionally.

Answer 4

There are only a few chords that really function as a V, i.e. that have a dominant function. Other answers interpreted your question more like "which chords can lead to the I chord", which is actually a different question, because you don't need a chord functioning as a dominant to get back to the I chord (e.g., plagal cadence).

These are the chords that can have a dominant function leading to the I (in the key of C major):

• G7 (and its variations like G7sus4, G9, etc.)
• Db7 (tritone sub)
• Bo (diminished triad, vii dim)
• Bo7 (diminished seventh chord, and all its inversions: Do7, Fo7, Abo7)

There is a huge number of other chords that resolve to the I chord without a dominant function. A few common examples are (again in the key of C major):

F  -> C
Fm -> C
Db(maj7) -> C
Bb7 -> C
D#07 -> C/E
F#o7 -> C/G

There are many more, but these are the ones that I encounter most frequently (in jazz/popular music). Of course, many of those chords are not purely diatonic chords, but they are used in the key of C major and they also resolve to the I chord (the same is true for some chords with a dominant function).

Answer 5

All chords whose root is V or VII are considered dominant chords, and are interchangeable: V major triad, dominant 7, minor and major dominant 9th (minor 9th in a major scale is common. Major 9th in a minor scale is rare), +11 and 13th. For the VII: diminished triad, diminished 7th, semi-diminished 7th (rare in minor scale). Some of these work as altered too: G7 can have d#, db, or both. Pop uses a lot of triads. Blues dominant 7 everywhere. Jazz all kinds of extensions and altered. Classical, too, depending on period and composer: Mozart, usually dominant 7, while altered and substitution is common in Mahler and Wagner.