In music, a ninth is a compound interval consisting of an octave plus a second.^[1] Like the second, the interval of a ninth is classified as a dissonance in common practice tonality. Since a ninth is an octave larger than a second, its sonority level is considered less dense.^[2]

Major ninth

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A major ninth is a compound musical interval spanning 14 semitones, or an octave plus 2 semitones. For instance, the interval between C₄ and D₅ (in scientific pitch notation) is a major ninth.

If transposed into a single octave, it becomes a major second or minor seventh. The major ninth is somewhat dissonant in sound.

Minor ninth

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A minor ninth (m9 or -9) is a compound musical interval spanning 13 semitones, or 1 semitone above an octave (thus it is enharmonically equivalent to an augmented octave). For instance, the interval between C₄ and D♭₅ (in scientific pitch notation) is a minor ninth.

If transposed into a single octave, it becomes a minor second or major seventh. The minor ninth is rather dissonant in sound,^[3] and in European classical music, often appears as a suspension.

The fourth movement (an intermezzo) of Robert Schumann's Faschingsschwank aus Wien is constructed to feature prominent notes of the melody a minor ninth above the accompaniment:

Béla Bartók wrote a study in minor ninths for piano. Several of Igor Stravinsky's works open with a striking gesture that includes the interval of a minor 9th, either as a chord, as in Les noces and Threni, or as an upward melodic leap, as a in Capriccio for Piano and Orchestra, Symphony in Three Movements, and Movements for Piano and Orchestra.

Augmented ninth

An augmented ninth is a compound musical interval spanning 15 semitones, or 3 semitones above an octave. For instance, the interval between C₄ and D♯₅ (in scientific pitch notation) is a major ninth.

Enharmonically equivalent to a compound minor third, if transposed into a single octave, it becomes a minor third or major sixth.

See also

• Augmented octave
• Augmented unison

References