Types of seventh chord in the key of C.
In all, there are ten usable kinds of seventh chords, although some of these are only rarely encountered. The three most commonly used sevenths are the dominant seventh, the major seventh, and the minor seventh.
Why are there so many different kinds of seventh chord?
The wide variety of seventh chords stems from the fact that there are different kinds of triad (major, minor, diminished, augmented) and also different kinds of seventh (major, minor, diminished). These can be combined in a lot of different ways. For example, the root note can be combined with a minor 3rd, a perfect 5th (a minor triad), and a minor 7th to give a minor 7th chord. Or, the root can be combined with a minor 3rd, a perfect 5th, and a major 7th to give what's called a minor/major 7th.
The ten different kinds of seventh chord are identified below, using the key of C as an example.
These ten types of seventh chord fall into three distinct families: the dominant seventh, the major seventh, and the minor seventh.
Also known as the major-minor seventh, a chord composed of a root, major third, perfect fifth, and minor seventh. It can also be viewed as a major triad with an added minor seventh. Of all the seventh chords, the dominant seventh is perhaps the most important. In popular music, it is denoted by adding a '7' after the letter designating the chord root.
The dominant seventh was the first seventh chord to appear regularly in classical music. The name comes from the fact that it occurs naturally in the seventh chord built upon the dominant (i.e. the fifth degree) of a given major diatonic scale. Consider for example the scale of D major: D, E, F♯, G, A, B, and C♯. The fifth note – the dominant – is A. The major triad built from this is A C ♯ E. Adding a minor 7th (G) on top of this gives the A7 chord: A C ♯ E G.
The dominant seventh itself is one of three chords in the dominant seventh family all derived from major triads plus minor sevenths. The other two are the seventh augmented fifth (or 'seventh sharp five') and the seventh diminished fifth (or 'seventh flat five').
The major seventh chord is composed of a root, major third, perfect fifth, and major seventh. So, it differs from the dominant seventh in only one note – the seventh note being a half-tone higher. The major seventh itself is one of four chords in the major seventh family, all distinguished from other types of seventh chord by having an interval of a major seventh between their lowest and highest notes. The others are the minor/major seventh, the major seventh diminished fifth (or 'major seventh flat five"), and the major seventh augmented fifth (or 'major seventh sharp five").
Fingerings for the major 7th chords in open position on the guitar are shown below.
The minor seventh chord is composed of a root, minor third, perfect fifth, and minor seventh. It is one of three chords in the minor seventh family, the others being the half-diminished seventh (or 'minor seventh diminished fifth') and the diminished seventh.
A comparison of the dominant, major, and minor seventh
A quick glance at the chord charts for three different sevenths chords in the key of D – D major 7, D minor 7, and D7 (dominant) – suggests that there's not much difference between them. But this is deceptive.
A major 7th consists of root + major 3rd + perfect 5th + major 7th. For example, Dmaj7 = D + F♯ + A + C♯.
A minor 7th consists of root + minor 3rd + perfect 5th + minor 7th. For example, Dm7 = D + F + A + C.
A dominant 7th consists of root + major 3rd + perfect 5th + minor 7th. For example, D7 = D + F♯ + A + C.