A seventh chord is a four-tone, in the basic form of which the sounds are arranged in thirds, that is, a triad with a third added on top. A characteristic feature of the seventh chord is the seventh interval between the extreme sounds of the chord, which, together with the triad, which is part of the seventh chord, determines its appearance.
The following seventh chords are distinguished: a major major, consisting of a major triad with a large seventh, a small major – from a major triad with a small seventh, a small minor – from a minor triad with a small seventh, a small introductory – from a diminished triad with a small seventh, a diminished introductory – from a reduced triads with diminished seventh; seventh chords with an augmented fifth – a major minor, consisting of a minor triad with a major seventh, and a seventh chord of an augmented triad with a major seventh. The most common seventh chords are: dominant seventh chord (small major), denoted by V7 or D7, is built on the V Art. major and harmonic. minor; small introductory (m. VII7) – on the VII Art. natural major; reduced introductory (d. VII7) – on the VII Art. harmonic major and harmonic. minor; subdominant S. – on the II century. natural major (small minor, m. m. II7 or II7), on II Art. harmonic major and both types of minor (small with a reduced triad, or small introductory S. – m. v. II7). The seventh chord has three appeals: the first is the quint-sext chord (6/5) with a terts tone in the lower voice, the second is a terzkvartakkord (3/4) with a fifth tone in the lower voice, the third is a second chord (2) with a seventh in the lower voice. The most commonly used are the dominants of the seventh chord and the quintsextachord of the subdominant of the seventh chord (II7). See Chord, Chord inversion.
V. A. Vakhromeev