Dominant seventh chord

Of all the seventh chords, perhaps the most important to understand is the 'dominant seventh' , a major triad

Major chord

In music theory, a major chord is a chord having a root, a major third, and a perfect fifth. When a chord has these three notes alone, it is called a major triad...

 with a minor seventh

Minor seventh

A minor seventh is the smaller of two commonly occurring musical intervals that span seven diatonic scale degrees. The prefix 'minor' identifies it as being the smaller of the two , its larger counterpart being a major seventh. The minor seventh is abbreviated as m7 and its inversion is the major...

. It was the first seventh chord to appear regularly in Western music

Western music

Western music is the genres of music originating in the Western world including Western classical music, American Jazz, Country and Western, pop music and rock and roll...

. The name comes from the fact that it occurs naturally in the seventh chord

Seventh chord

A seventh chord is a chord consisting of a triad plus a note forming an interval of a seventh above the chord's root. When not otherwise specified, a "seventh chord" usually means a major triad with a flat seventh...

 built on the dominant (fifth)

Dominant (music)

In music, the dominant is the fifth degree of a musical scale. The dominant has the role of creating instability that requires the tonic or goal-tone for release....

 scale degree of a given major key

Key (music)

In music theory, the term key is used in many different and sometimes contradictory ways. A common use is to speak of music as being "in" a certain key, such as in the key of C or in the key of F-sharp. Sometimes the terms "major" or "minor" are appended, as in the key of A minor or in the key of...

.

Take for example the key of C major:



The note G is the dominant degree of C major (C, D, E, F, G, A, B, C) - the fifth note of the major scale whose first note is C (the dominant degree of any major key is always the fifth note).

Of all the seventh chords, perhaps the most important to understand is the 'dominant seventh' , a major triad

Major chord

In music theory, a major chord is a chord having a root, a major third, and a perfect fifth. When a chord has these three notes alone, it is called a major triad...

 with a minor seventh

Minor seventh

A minor seventh is the smaller of two commonly occurring musical intervals that span seven diatonic scale degrees. The prefix 'minor' identifies it as being the smaller of the two , its larger counterpart being a major seventh. The minor seventh is abbreviated as m7 and its inversion is the major...

. It was the first seventh chord to appear regularly in Western music

Western music

Western music is the genres of music originating in the Western world including Western classical music, American Jazz, Country and Western, pop music and rock and roll...

. The name comes from the fact that it occurs naturally in the seventh chord

Seventh chord

A seventh chord is a chord consisting of a triad plus a note forming an interval of a seventh above the chord's root. When not otherwise specified, a "seventh chord" usually means a major triad with a flat seventh...

 built on the dominant (fifth)

Dominant (music)

In music, the dominant is the fifth degree of a musical scale. The dominant has the role of creating instability that requires the tonic or goal-tone for release....

 scale degree of a given major key

Key (music)

In music theory, the term key is used in many different and sometimes contradictory ways. A common use is to speak of music as being "in" a certain key, such as in the key of C or in the key of F-sharp. Sometimes the terms "major" or "minor" are appended, as in the key of A minor or in the key of...

.

Take for example the key of C major:



The note G is the dominant degree of C major (C, D, E, F, G, A, B, C) - the fifth note of the major scale whose first note is C (the dominant degree of any major key is always the fifth note). When we arrange the notes of the C major scale in ascending pitch and use only these notes to build a seventh chord, and we start with G (not C), then the resulting chord, containing the four notes GBDF and called G7, is a major triad, GBD, with a dominant (minor) seventh, F (that is, from G to F includes seven notes).

This basic dominant seventh chord is useful to composers because it contains both a major triad and the interval of a tritone

Tritone

The tritone is a musical interval that spans three whole tones. The tritone, sometimes known as the Diabolus in Musica, is the same as an augmented fourth, which in 12-tone equal temperament is enharmonic to a diminished fifth...

. The major triad confers a very "strong" sound. The tritone is created by the cooccurrence of the third degree and seventh degree (e.g., in the G7 chord, the acoustic distance between B and F is a tritone). In a diatonic context, the third of the chord is the leading-tone

Leading-tone

In music theory, a leading-note is a note or pitch which resolves or "leads" to a note one semitone higher or lower, being a lower and upper leading-tone, respectively....

 of the scale, which has a strong tendency to pull towards the tonal center, or root note, of the key (e.g. the third of G7, B, is the leading tone of the key of C). This, in combination with the strength of root movement by fifth

Counterpoint

In music, counterpoint is the relationship between two or more voices that are independent in contour and rhythm and are harmonically interdependent. It has been most commonly identified in Western music, developing strongly during the Renaissance and in much of the common practice period,...

, and the natural resolution of the dominant triad to the tonic triad (e.g., from GBD to CEG in the key of C major), creates a resolution with which to end a piece or a section of a piece. Because of this original usage, it also quickly became an easy way to trick the listener's ear with a deceptive cadence.

However, the most important use of the dominant seventh chord in musical composition is the way that the introduction of a non-diatonic dominant seventh chord (sometimes called a chromatic seventh), which is borrowed from another key, can allow the composer to modulate

Modulation (music)

In music, modulation is most commonly the act or process of changing from one key to another. This may or may not be accompanied by a change in key signature. Modulations articulate or create the structure or form of many pieces, as well as add interest...

 to that other key. This technique is extremely common, particularly since the classical period, and has led to further innovative uses of the dominant seventh chord such as secondary dominant

Secondary dominant

Secondary dominant is a type of chord used in musical harmony. It refers to a dominant of a degree other than the tonic, with V7/V, the dominant of the dominant, "being the most frequently encountered". The chord to which a secondary dominant progresses is a tonicized chord in that it is briefly...

, extended dominant

Extended dominant

An extended dominant is a non-diatonic dominant 7th chord that resolves downwards to another dominant chord. A series of extended dominant chords continues to resolve downwards by perfect 5ths until they reach the tonic chord....

, and substitute dominant chords.

The dominant seventh is frequently used to approximate a Harmonic seventh

Harmonic seventh

The harmonic seventh interval , also known as the septimal minor seventh, or subminor seventh, is one with an exact 7:4 ratio . This is somewhat narrower than and is "sweeter in quality" than an "ordinary" minor seventh, which has a just-intonation ratio of either 16:9 or 9:5, or an...

.

See also: irregular resolution