ABSTRACT
The fully diminished seventh chord, vii°7, is said to be symmetrical because it is constructed entirely of a single interval, the minor third. Even the augmented second between the seventh of the chord and the root is enharmonic to a minor third. Its symmetry renders the °7 chord ambiguous, in that it is truly impossible to determine the root of this chord by ear. Symmetry makes the °7 chord ideal for modulation because it can resolve to four different chords. The common-tone °7 (ct°7) is a non-functional embellishing chord in which every note of the chord except for one is a neighbor tone to the chord before and after it. The root of the chord that is being embellished is held in common with one of the notes of the °7—hence the name of the chord.
