Mediant

What it means

Mediant, in the naming of scale degrees, designates the third degree of a key, which lies in the middle between tonic and dominant — hence the name. In C major that is E and the E minor triad built on it (III). In German-language harmony the word additionally has a second, broader meaning, which is encountered more often in practice.

Musical use

In the narrower meaning, the mediant is a secondary sonority belonging to the scale. In terms of function theory, the triad on the third degree is interpreted, depending on context, as a tonic counter-chord or as the dominant's relative, because it shares two notes with each. It is used more rarely than the other secondary degrees and appears above all in sequences and as a passing sonority.

In the broader meaning, any sonority whose root lies a third above or below a reference sonority is called a mediant, even if it lies outside the scale. Especially effective are chromatic mediants, in which the two sonorities share only one note or none at all — for instance C major and E major, or C major and A♭ major. Such third-relationships became a favoured means of colour in the nineteenth century: they seem surprising and radiant, because they avoid the customary fifth relationships, and they suit abrupt changes of key without a mediating modulation.

The mediant is to be distinguished from the submediant, which in the naming of degrees designates the sixth degree — a third below the tonic.

In German usage the term has two meanings. It designates, on the one hand, the third degree of a key, and on the other, chords at a third's distance from the tonic, which are called mediants or third-relations. In the harmony of the Romantic era such third-relationships play a large role, because they allow surprising changes of colour.

Performance practice

If a piece moves into a sonority related by a third, shape the change as a change of colour and not as a cadence — it should shine, not close. Watch the intonation of the notes that change with the shift; with chromatic mediants, usually the shared note shifts in its meaning. And distinguish the two meanings of the word in analysis.