Seventh Chord - Types of Seventh Chords

Types of Seventh Chords

Most textbooks name these chords formally by the type of triad and type of seventh; hence, a chord consisting of a major triad and a minor seventh above the root is referred to as a major/minor seventh chord. When the triad type and seventh type are identical (i.e. they are both major, minor, or diminished), the name is shortened. For instance, a major/major seventh is generally referred to as a major seventh. This rule is not valid for augmented chords: since the augmented/augmented chord is not commonly used, the abbreviation augmented is used for augmented/minor, rather than augmented/augmented. Additionally, half-diminished stands for diminished/minor, and dominant stands for major/minor. When the type is not specified at all, the triad is assumed to be major, and the seventh is understood as a minor seventh (e.g. a "C" chord is a "C major triad", and a "C7" chord is a "C major/minor seventh chord", also known as a "C dominant seventh chord").

The most common chords are tertian, constructed using a sequence of major thirds (spanning 4 semitones) and/or minor thirds (3 semitones). Seven tertian seventh chords are commonly found in western music:

The following seventh chord is not tertian, as it is built using a sequence of two major thirds (4 semitones) and a diminished third (2 semitones, enharmonically equivalent to a major second):

• Augmented seventh (formally augmented/minor seventh, also aug7, +7, etc.): root, major third, augmented fifth, minor seventh
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The following seventh chord is again not tertian, as it is built using a sequence of two minor thirds (3 semitones) and an augmented third (5 semitones, enharmonically equivalent to a perfect fourth):

• Diminished major seventh (also mM7♭5, -Δ7♭5, etc.): root, minor third, diminished fifth, major seventh
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In tuning systems other than equal temperament there are further possible seventh chords. In just intonation, for example, there is the harmonic seventh.