Common tone (chord)


In music, a common tone is a pitch class that is a member of, or common to two or more chords or sets. Typically, it refers to a note shared between two chords in a chord progression. According to H.E. Woodruff:
The example below shows the seven diatonic triads of C major. The common tones between the tonic triad and the other six triads are highlighted in blue. As Woodruff describes, the tonic triad shares no common tones with either II and VII, one common tone with IV and V each, and two common tones with III and VI each.

In voice leading

Common tones are a consideration in voice leading and voicing. Abbé Vogler, Weber, Hauptmann, A. B. Marx, and earlier theorists emphasized "common-tone retention and smooth voice leading in... treatment of harmonic succession ". It may be considered a guideline or a rule.
The example below shows a circle progression in C major, in which common tones are retained in the second voice.

Common-tone diminished seventh chord

A diminished seventh chord may resolve to a chord whose root is common to both chords. When this happens, the first chord is called a common-tone diminished seventh chord.