Major sixth

What it means

The major sixth comprises nine semitones and arises through inversion of the minor third: if one places the lower note of a minor third an octave higher, a major sixth results. The rule behind it holds generally — the numbers of two inverted intervals add up to nine, and major becomes minor, minor becomes major.

Musical use

As an imperfect consonance the sixth may be led in parallel, and parallel sixths belong to the familiar stock of polyphonic writing. The faux-bourdon of the fifteenth century rests on this sonority. In sound the major sixth seems open and warm, less dense than the third.

In the chord it appears in several places. The first-inversion chord, that is, the first inversion of the triad, has third and sixth above the bass; whether the latter is major or minor depends on the mode. The sixte ajoutée adds a sixth instead of a seventh to a triad and thereby sounds softer, often at the ending. And the augmented sixth chord, a formation with particular tension, builds on an extended form of this interval.

Melodically the major sixth is a wide but easily singable leap that often leads upward to the peak note of a phrase and is then led back stepwise.

In melody the major sixth is an expressive upward leap that occurs in many song openings and acts wide and opening. Harmonically it counts among the imperfect consonances. In writing, parallel sixths are used like parallel thirds, because they leave the voices independence and yet sound pleasing. In the fauxbourdon, parallel sixths between upper and lower voice determine the sound, and in brass writing they are a favoured means for warm two-part texture.

Performance practice

Sing the sixth by a detour if it is hard for you: think it as a fifth plus a whole tone or derive it from a triad. Intonate it rather wide, similar to the way the major third is taken low — both follow the same acoustic reason. And lead the line back after a leap of a sixth; in this way the phrase stays in balance.