Minor sixth

Overview

The minor sixth is a diatonic interval that spans eight semitones, or three whole tones plus two half steps. In 12‑tone equal temperament it measures exactly 800 cents, while in just intonation its most common ratio is 8:5 (approximately 814 cents). It is classified as a consonant interval, though it is less stable than the perfect fifth or octave, giving it a slightly plaintive or yearning character.

When notated, the minor sixth is identified by the number six together with the quality “minor” (e.g., C to A♭). It can appear as a melodic leap, as part of a harmonic chord (such as a minor sixth chord), or as an intervallic component of larger structures like thirteenth chords.

History / Origin

The term derives from the Latin minor sextus, meaning “smaller sixth,” contrasting with the “major sixth.” The concept of the sixth interval dates back to ancient Greek theory, where it was considered a “diatonic” step. In medieval modal theory the sixth was treated as an imperfect consonance, and the distinction between major and minor qualities emerged during the Renaissance as composers began to employ accidentals more freely. The minor sixth entered common‑practice harmony in the Baroque era, where it was used both melodically and in chordal structures.

How It’s Used

In classical repertoire the minor sixth frequently appears as a melodic leap, often signalling expressive tension that resolves downward. In harmony, the interval forms the basis of the minor sixth chord (a minor triad with an added sixth) and is a component of the dominant thirteenth chord. Jazz musicians exploit the minor sixth as a “blue note” interval, incorporating it into improvisational lines and chord extensions. The interval is also prevalent in folk music, where it contributes to the characteristic lamenting quality of many ballads.

Why It Matters

The minor sixth’s unique emotional color makes it a valuable tool for composers and arrangers seeking to convey melancholy, longing, or surprise. It is audible in the opening leap of the Gregorian chant “Dies irae,” where the melody rises a minor sixth from D to B♭, creating a stark, foreboding effect. In popular music, the interval is often used in vocal harmonies and melodic hooks, adding richness without the brightness of a major sixth.

Common Misconceptions

Because interval names are similar, the minor sixth is sometimes confused with other sixths or with compound intervals.

• Misconception: A minor sixth is the same as a major sixth.
  Correction: A major sixth spans nine semitones (900 cents) and is one whole tone larger than a minor sixth.
• Misconception: A minor sixth is the same as a compound sixth (13th).
  Correction: A compound sixth, or thirteenth, adds an octave to a sixth, resulting in a total span of 20 semitones, not eight.
• Misconception: The minor sixth is always dissonant.
  Correction: In common‑practice harmony the minor sixth is considered a consonant interval, though it carries a softer, more ambiguous tension than perfect intervals.