In music, the submediant is the sixth degree () of the diatonic scale, the lower mediant--halfway between the tonic and the subdominant ("lower dominant"). In the movable do solfège system, the submediant note is sung as la in major, as fa in minor. It is occasionally called superdominant, as the degree above the dominant. This is its normal name (sus-dominante) in French.
The triad formed on the submediant note is the submediant chord. In Roman numeral analysis, the submediant chord is typically symbolized by the Roman numeral "VI" if it is major and by "vi" if it is minor.
The term submediant may also refer to a relationship of musical keys. For example, relative to the key of C major, the key of A minor is the submediant. In a major key, the submediant key is the relative minor and has the same notes as the original major key. Modulation (change of key) to the submediant is relatively rare, compared with modulation to the dominant in a major key or modulation to the mediant in a minor key.
In major, the submediant chord also often appears as the starting point of a series of perfect descending fifths and ascending fourths leading to the dominant, vi-ii-V. This is because the relationship between vi and ii and between ii and V is the same as that between V and I. If all chords were major (I-VI-II-V-I), the succession would be one of secondary dominants. This submediant role is as common in popular and classical music as it is in jazz, or any other musical language related to Western European tonality. A more complete version starts the series of fifths on the chord of iii, iii-vi-ii-V-I, as in Charlie Parker's "Blues for Alice". In minor, the progression from VI to ii° (e.g. A♭-D in C minor) involves a diminished fifth, as does the ii° chord itself; it may nevertheless be used in VI-ii°-V-I by analogy with the major. Similarly, the full circle progression I-IV-vii°-iii-vi-ii-V-I can be used by analogy with the usual descending fifth progression, even although IV-vii° involves a diminished fifth.
Another frequent progression is the sequence of descending thirds (I-vi-IV-ii-|-V in root position or first inversion), alternating major and minor chords. This progression is also frequent in jazz, where it is used in a shortened version (I-vi-IV-V) in the "ice cream change", which moves from the tonic through the submediant and subdominant on the way to the dominant.
Chromatic submediants, like chromatic mediants, are chords whose roots are related by a major third or minor third, contain one common tone, and share the same quality, i.e. major or minor. They may be altered chords.
The term mediant appeared in English in 1753 to refer to the note "midway between the tonic and the dominant". The term submediant must have appeared soon after to similarly denote the note midway between the tonic and the subdominant. The German word Untermediante is found in 1771. In France, on the other hand, the sixth degree of the scale was more often called the sus-dominante, as the degree above the dominant. This reflects a different conception of the diatonic scale and its degrees:
In the German theory derived from Hugo Riemann, the minor submediant in a major key is considered the Tonikaparallele (minor relative of the major tonic), labeled Tp, and the major submediant in a minor key is the Subdominantparallele (major relative of the minor subdominant), labeled sP.