Common chord (music)

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Common chord in the keys of G, D, and A major; as well as E, B, and F♯ minor.

A common chord, in the theory of harmony, is a

diatonic to more than one key or, in other words, is common to (shared by) two keys.[1] A "common chord" may also be defined simply as a triadic chord[2] (e.g., C–E–G), as one of the most commonly used chords in a key (I–IV–V–vi–ii–iii),[3] more narrowly as a triad in which the fifth is perfect (i.e., a major or minor triad), in which sense it is alternatively referred to as a "perfect chord"[4][5] or, more narrowly still (in American practice[6][7]), as a major triad only.[8]

Common chords are frequently used in modulations, in a type of modulation known as common chord modulation or diatonic pivot chord modulation. It moves from the original key to the destination key (usually a closely related key) by way of a chord both keys share. For example, G major and D major have 4 chords in common: G, Bm, D, Em. This can be easily determined by a chart similar to the one below, which compares chord qualities. The I chord in G major—a G major chord—is also the IV chord in D major, so I in G major and IV in D major are aligned on the chart.

C major: V vi viio I ii iii IV
G major: I ii iii IV V vi viio
D major: IV V vi viio I ii iii

Any chord with the same

function
in both the original and the destination keys, as it can be seen either way.

A chord is common to, or shared by, six keys: three major keys, and three relative minor keys. For example, a C major chord is contained in F, C, and G major as well as D, A, and E minor.

Related keys

The number of diatonically occurring chords that two keys share is a measure of how closely related they are. A

relative major or minor key has all of its chords in common; a dominant or subdominant
key has four in common. Less closely related keys have two or fewer chords in common.

For example, C major and A minor have 7 common chords while C major and F♯ major have 0 common chords.

C CEG DFA EGB FAC GBD ACE BDF
F CEG DFA EGB♭ FAC GB♭D ACE B♭DF
G CEG DF♯A EGB F♯AC GBD ACE BDF♯
D C♯EG DF♯A EGB F♯AC♯ GBD AC♯E BDF♯
B♭ CE♭G DFA E♭GB♭ FAC GB♭D ACE♭ B♭DF

See also

References

  1. ISBN 978-0-07-294262-0
    .
  2. ^ Johnson, A. N. (Artemas Nixon) (1855). Practical instructions in harmony, upon the Pestalozzian or inductive system; teaching musical composition and the art of extemporizing interludes and voluntaries. University of California Libraries. Boston: Oliver Ditson and Company. p. 5. A common chord is composed of three letters, so arranged that the second letter is at the interval of a third, and the third letter at the interval of a fifth, from the first letter.
  3. ISBN 978-0-02-864155-3
    .
  4. ^ "chord". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.), entry "chord, n.2", sense 3.a.
  5. ISBN 9780198614593
    .
  6. ISBN 978-0-19-866212-9
    .
  7. ISBN 9780195170672
  8. ISBN 978-0-674-01163-2
    . "Common chord: Major triad."
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