The third scale degree of a diatonic scale

In music theory, the "mediant" is a term used to describe the third degree of a diatonic scale, typically represented by the Roman numeral "III" when analyzing harmonic progressions. The mediant note is located halfway between the tonic (first degree) and the dominant (fifth degree) of the scale. It plays a significant role in shaping the harmonic and melodic character of a piece of music. For example:

  • In the key of C major, the mediant note is E.
  • In the key of A minor, the mediant note is C.

The mediant note has a unique quality that can be characterized as "mediating" between the stability of the tonic and the tension of the dominant. Harmonically, the mediant chord, often denoted as "iii" (minor) or "III" (major), is built upon the mediant note.

  • In C major, the iii chord is E minor (E, G, B).
  • In A minor, the III chord is C major (C, E, G).

The mediant chord adds variety and color to harmonic progressions, creating different emotional nuances compared to the tonic and dominant chords. It can serve as a point of departure or a moment of repose within a piece of music.

Melodically, the mediant note is important for crafting interesting and expressive melodies. Its position between the tonic and dominant allows for smooth and melodic transitions within a scale. Melodies often make use of the mediant to add variety and direction to their phrases.

Harmonically, the mediant chord can be used to introduce a change of tonal color or mood. It can create a sense of modulation or tonal exploration, leading to unexpected harmonic twists and turns.

Example of Mediant

Lesson 21: Scale Degrees. What are they?