These chords may also appear as seventh chords: in major, as ii7 (in C: D–F–A–C), while in minor as iiø7 (in C: D–F–A♭–C) or rarely ii7. They are the second-most-common form of nondominant seventh chords.[2]
The supertonic chord normally functions as a
dominant function. The supertonic chord lies a fifth above the V chord. Descending fifths are a strong basis for harmonic motion (see circle of fifths
). The supertonic is one of the strongest predominants and approaches the V chord from above by descending fifth.
In major or minor, the major chord built on the lowered supertonic (♭
common-tone diminished seventh chord, ♯iio7 (in C: D♯–F♯–A–C). One variant of the supertonic seventh chord is the supertonic diminished seventh[3] with the raised supertonic, which equals the lowered third through enharmonic equivalence
(in C: D♯=E♭).
The term supertonic may also refer to a relationship of musical keys. For example, relative to the key of C major, the key of D major (or D minor) is the supertonic.