Ninth chord in the context of Close and open harmony

In music, extended chords are certain chords (built from thirds) or triads with notes extended, or added, beyond the seventh. Ninth, eleventh, and thirteenth chords are extended chords. The thirteenth is the farthest extension diatonically possible as, by that point, all seven tonal degrees are represented within the chord (the next extension, the fifteenth, is the same as the root of the chord). In practice however, extended chords do not typically use all the chord members; when it is not altered, the fifth is often omitted, as are notes between the seventh and the highest note (i.e., the ninth is often omitted in an eleventh chord; the ninth and eleventh are usually omitted in a thirteenth chord), unless they are altered to give a special texture.

Chords extended beyond the seventh are rarely seen in the Baroque era, and are used more frequently in the Classical era. The Romantic era saw greatly increased use of extended harmony. Extended harmony prior to the 20th century usually has dominant function – as V, V, and V, or V/V, V/ii etc.

The first inversion of a chord is the voicing of a triad, seventh chord, or ninth chord in which the third of the chord is the bass note and the root a sixth above it. In the first inversion of a C-major triad, the bass is E — the third of the triad — with the fifth and the root stacked above it (the root now shifted an octave higher), forming the intervals of a minor third and a minor sixth above the inverted bass of E, respectively.

In the first inversion of G-dominant seventh chord, the bass note is B, the third of the seventh chord.

The second inversion of a chord is the voicing of a triad, seventh chord, or ninth chord in which the fifth of the chord is the bass note. In this inversion, the bass note and the root of the chord are a fourth apart which traditionally qualifies as a dissonance. There is therefore a tendency for movement and resolution. In notation form, it may be referred to with a c following the chord position (e.g., Ic. Vc or IVc). In figured bass, a second-inversion triad is a
₄ chord (as in I
₄), while a second-inversion seventh chord is a
₃ chord.

Note that any voicing above the bass is allowed. A second inversion chord must have the fifth chord factor in the bass, but it may have any arrangement of the root and third above that, including doubled notes, compound intervals, and omission (G-C-E, G-C-E-G', G-E-G-C'-E', etc.)

In music, the dominant is the fifth scale degree () of the diatonic scale. It is called the dominant because it is second in importance to the first scale degree, the tonic. In the movable do solfège system, the dominant note is sung as "So(l)".

The triad built on the dominant note is called the dominant chord. The chord is said to have dominant function, which means that it creates an instability that requires the tonic for resolution. Dominant triads, seventh chords, and ninth chords typically have dominant function. Leading-tone triads and leading-tone seventh chords may also have dominant function.