31 Tone Equal Temperament

Intervals: 6 : Septimal Whole Tone

The septimal whole tone is a musical interval not found in most western music. It corresponds to the difference between the 7th and 8th harmonics, and is wider than a standard whole tone, and narrower than a minor third. Harmonically, the septimal whole tone can function both as dissonance and consonance, depending on context; it tends to be less dissonant than a whole tone but more so than most of the thirds.

Melodic use of the septimal whole tone

The septimal whole tone exists in an intermediate area between scale steps and familiar harmonic intervals like thirds: it is narrow enough that it can sometimes be perceived as a single step of a scale, but wide enough that it can be perceived as a larger leap or jump. All narrower intervals in 31-ET, from the whole tone down, tend to be perceived as a single step, whereas larger ones tend to be perceived as a jump or leap.

The perception of this interval as a single step or something greater depends greatly on context.

Root of a Septimal Whole Tone:

The septimal whole tone has the interesting property that it implies the top note, rather then the bottom note, as a root. Its harmonic function is thus very different from a normal whole tone, which tends to imply the bottom note as root.