The next note in the order of extended harmonies is the ninth. Ninths are construed three different ways. First, there is the major (or natural) ninth. This is used in conjunction with any of the sevenths mentioned previously. Basically, the ninth supports and amplifies the color of whatever seventh is used over the triad (major or minor). Sometimes the ninth is used minus the seventh. In this case the ninth has a less jazzy sound and instead evokes a more pop-oriented feeling. This usage of the ninth is also called add 2. The other ways that you'll see a ninth configured are as a sharp nine (#9) or a flat nine (9, especially in minor keys (keys where the i is minor). In fact, if you intend to add a ninth extension in a minor key, it generally is a sharp or flat nine, not a major or natural nine. Superscript numerals can also be used to denote ninth extensions.

Sharp and flat nines are functionally equivalent. This means that both attach themselves interchangeably to dominant seventh chords in their functional role as V chords, often in a minor key. Color-wise, however, sharp and flat nines both have different aesthetical qualities. The sharp nine tends to be edgier, bluesier, and meaner sounding. On the other hand, the flat nine tends to be sweeter and prettier, albeit melancholy. Ballads may be more appropriate for flat nines while funkier, more Afrocentric jazz (like 1960s-era John Coltrane or Miles Davis) tends to demand the energy and unsettled feel of a sharp nine. See Figure 17-7 where both sharp and flat nines are employed as V chords going to minor i and major I chords.

Figure 17-7.

Sharp and flat nines followed by minor i and major I chords

Notice the key changes and chord functions!