Like the second, the interval of a ninth is classified as a dissonance in common practicetonality. Since a ninth is an octave larger than a second, its sonority level is considered less dense.[1]
A major ninth is a compound musical interval spanning 14 semitones, or an octave plus 2 semitones. If transposed into a single octave, it becomes a major second or minor seventh. The major ninth is somewhat dissonant in sound.
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). If transposed into a single octave, it becomes a minor second or major seventh. The minor ninth is rather dissonant in sound,[2] and in European classical music, often appears as a suspension. Béla Bartók wrote a study in minor 9ths for piano. 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:
An augmented ninth is a compound musical interval spanning 15 semitones, or 3 semitones above an octave. Enharmonically equivalent to a compound minor third, if transposed into a single octave, it becomes a minor third or major sixth.
Dominant ninth chord on C. PlayⓘMajor ninth chord on C. PlayⓘMinor ninth chord on C. Playⓘ
Three types of ninth chords may be distinguished: dominant (9), major (M9), and minor (m9).[3][4] They may easily be remembered as the chord quality of the seventh does not change with the addition of the second scale degree,[3] which is a major second in both major and minor, thus:
0 4 7 t + 2 = dominant seventh + ninth = dominant ninth chord
0 4 7 e + 2 = major seventh + ninth = major ninth chord
0 3 7 t + 2 = minor seventh + ninth = minor ninth chord
The dominant ninth (V9) is a dominant seventh plus a major or minor ninth.[5]
^ abBruce Buckingham, Eric Paschal (2001). Rhythm Guitar: The Complete Guide, p.58. ISBN978-0-7935-8184-9.
^Michael Miller (2004). Complete Idiot's Guide to Solos and Improvisation, p.51. ISBN978-1-59257-210-6.
^Helen S. Leavitt (1916). Practical Lesson Plans in Harmony, p.32. Ginn and Company. "In major keys the dominant ninth is usually major, though occasionally it is chromatically altered to a minor. In minor keys a similar chromatic change from minor to major takes places."