In music, the supertonic is the second degree (
The triad built on the supertonic note is called the supertonic chord. In Roman numeral analysis, the supertonic chord is typically symbolized by the Roman numeral "ii" in a major key, indicating that the chord is a minor chord (in C: D–F–A). In a minor key, it is indicated by "iio" if it is built on the a natural minor scale, indicating that the chord is a diminished chord (in C: D–F–A♭). Because it is a diminished chord, it usually appears in first inversion (iio6) so that no note dissonates with the bass note.
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.
The supertonic chord normally functions as a predominant chord, a chord that naturally resolves to chord with 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 (♭
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.
In Riemannian theory, the supertonic is considered the subdominant parallel: Sp/T in major though sP/T in minor (A♭M).