Suomeksi | In English

Common-tone diminished seventh chords

A tonic chord can be accompanied by a diminished four-note chord with the tonic. A dominant chord (often dom7) can also be preceded by a chord resembling a secondary dominant (VII/) but including a dominant note. These chords are called common-tone diminished seventh chords.

In standard voice leading, one of the notes in the chord stays and one of the diatonic notes progresses by degrees. Two chromatically altered notes tend strongly to resolve into their main note: # and # into the third and fifth of the tonic chord, # and # into the third and fifth of the dominant chord.

A chromatic chord is difficult to analyse; piles of thirds result in chords with two alternative root notes, II or VI degree. Common-tone diminished seventh chords can also be inverted, which will result in complex symbols. Occasionally, a chord may be written enharmonically, which may lead us to analyse the chord as a pile of thirds with another root note (bars 3 and 6).

A common-tone diminished seventh chord can be interpreted as an irregular deceptive resolution (VII7 – VI) in a minor key; a standard deceptive resolution would be V7-VI. In other words, a diminished four-note chord building on a leading note will, in E minor, resolve into C major and, in B minor, into G major.

An embellishment by nature, it is often heard in the music of the Romantic era and in popular music.