Musical Composition, Theory and Songwriting/dominant ninth chord


Hi Clare why is the 5th of the dominant 9th chord omitted? Thanks!

Hello Garren, and thanks for being patient.

It's omitted in common-practice SATB harmony because you have five notes in the chord but only four parts, so one of the notes must be omitted, and the fifth is the only note that's expendable.

If we start by thinking about the dominant 7th, it's the triad formed on the dominant (which in major keys will be major, and in minor keys it'll also be major because of the sharpened leading note) with a minor 3rd added on top.  In SATB harmony the dominant 7th *always* resolves downwards, and the leading note *always* rises, so if we're in G major (get out of the habit of always thinking in C!) the dominant 7th chord is D-F#-A-C, the dominant 7th is C and whichever voice it's in will resolve to B and the leading note is F# and whichever voice it's in will resolve to G.  The same goes if we're in G minor - dominant 7th resolves to Bb and leading note resolves to G.  C to F# is a tritone and it's that tritone and its resolution that establishes your key - if you're modulating you may pass through a key but until you've included the new dominant 7th and its resolution you haven't actually modulated.

The dominant 9th is an extended chord consisting of the dominant 7th with an extra 3rd (major in major keys, minor in minor keys) added.  So if we're in F major the dominant 9th is C-E-G-Bb-D and if we're in F minor it's C-E-G-Bb-Db.  Now, we need the root (otherwise it's not a dominant - E-G-Bb is chord VII not chord V7), we need the 3rd as it's the leading note and has to rise, we need the dominant 7th as it has to resolve downward, and we need the added 9th by definition.  So the only note we can do without is the 5th.

Hope this helps.  

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Clare Redfarn


All aspects of the academic/theoretical side of music, including harmony, counterpoint, elementary composition, history, harmonic analysis, aural training, sightreading - the lot! Please note I'm not primarily a composer so I can't help with composition beyond what's required for Grade 8 theory or A'level. And don't ask me about psychoacoustics or music psychology as I have no knowledge of, nor interest in, either subject.


57 years as pianist (soloist and accompanist); 42 years as harpsichordist (soloist and continuist); 10 years as violinist and 6 years as bassoonist (youth orchestras/chamber groups); 45 years as piano teacher, coach in performance/interpretation (all ages, instruments and levels) and private tutor (mainly the old O'level, Grade VI+ ABRSM theory/practical musicianship, A'level and undergraduates); 20 years as ballet pianist (Cecchetti syllabus).

Member of Musicians' Union in Britain 1978-1989 and 1991-2009.

I've been writing professionally since I was 20 - too many programme notes to count over the years and a number of articles. Additionally, from 1996-2000 I was a Music Assessor for London Arts and as such regularly wrote critiques of concerts given by recipients of Arts Council funding.

MA in European Cultural Policy & Administration (Warwick University, 1994)
B Mus with Honours (London University, 1977)
Postgraduate Diploma in Arts Administration (City University, 1982)
Licentiate of Royal Academy of Music in Piano Teaching (1976)
Licentiate of Royal Academy of Music in Harpsichord Teaching (1978)

Studied RAM Junior School (1966-74), then as full-time student (1974-78).

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