An added ninth chord is a major triad with an added ninth – Cadd9 consists of C, E, G and D. Added ninth chords differ from other ninth chords because the seventh is not included.
The 7#9 chord is an extended dominant 7th chord with an augmented (sharpened) ninth. This chord form got its nickname because it was a favorite of Hendrix, who did a great deal to popularize its use in mainstream rock music.
Theoretically ninth chords are built with 5 notes called root (1), major third (3), perfect fifth (5), minor seventh (b7) and ninth (9). We will see that it is quite unusual to play these five notes together on the guitar.
A ninth is one more note. The octave. A second is two notes right beside each other. A ninth would have either the bottom note an octave lower, or the top note an octave higher.
A seventh chord contains the root, 3rd, 5th and flattened 7th notes of the parent major scale. To form a 9th chord we're adding in an extra note which is – you guessed it – the 9th degree of the parent major scale. So a C9 would contain the notes C, E, G, Bb and D.
Typically found in jazz, an eleventh chord also usually includes the seventh and ninth, and elements of the basic triad structure. Variants include the dominant eleventh (C11, C–E–G–B♭–D–F), minor eleventh (Cm11, C–E♭–G–B♭–D–F), and major eleventh chord (Cmaj11, C–E–G–B–D–F).
In a Western Music context, you can add a 2 or 9 to just about any chord. A true 9th chord also includes the flatted 7th. That chord is most commonly used as a dominant, so a G9 in the key of C, A9 in the key of D, F9 in the key of Bb, etc. The Dominant or V chord is most typically followed by the Tonic, or I.
Simply put, because the 8th, 10th, 12th, and 14th, are chord tones that are already present in the lower portion of the chord, not tensions that can be added like the 9th, 11th, and 13th.
Identifying chord extensions in scales
Well, in music theory, the 9 is technically the same as 2, 11 the same as 4 and 13 the same as 6. If you see a chord written with a 13, you should know you're looking for a scale which includes a 6th.
Introducing the ninth note
The eighth note is the same as the root note, one octave above. The ninth note is the same as the second note, one octave above.
In modern pop/jazz harmony, after the dominant thirteenth, a thirteenth chord (usually notated as X13, e.g. C13) contains an implied flatted seventh interval. Thus, a C13 consists of C, E, G, B♭, and A. The underlying harmony during a thirteenth chord is usually Mixolydian or Lydian dominant (see chord-scale system).
Seventh chords create a much fuller sound than triads and are used in jazz music to create richer harmonic progressions. There are 5 main types of seventh chord that you need to learn – major, minor, dominant, half diminished and diminished.
Seventh chords are essential in functional harmony for the role they play in dominant sevenths. The dominant seventh is the seventh chord built on the fifth degree of the scale. This relationship between tonic and dominant provides the sense of tension and release in functional harmony.
The E7#9 has become synonymous with Jimi Hendrix because he used the chord so effectively, especially in songs like Purple Haze. The construction of the chord is a dominant 7th with an added #9 interval.
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 ninth chord is a seventh chord with one extra note added. That note is called the 9th—which is the same thing as the 2nd scale degree, only an octave higher. In the key of C, the 2nd scale degree is D. Therefore, the 9th scale degree is also D.
With the theoretical chord F–A–C–E–G–B the fundamental bass would be considered C, while the supposed bass would be F. Thus the notes F and A are added below a seventh chord on C, C–E–G–B, triadically (in thirds). This is also referred to as the "H chord".
Great example: Nirvana's “In Bloom.” Kurt Cobain wrote almost exclusively with power chords and, as a result, his songs use some very unusual chord progressions, often changing modes at the drop of a proverbial hat.
Most instruments (e.g., saxophone, trumpet, trombone, human voice) can only play one note at a time and, therefore, can't play chords; these are referred to as single-note instruments.
A ninth chord is created by adding a ninth to a seventh chord. The most common ninth chords are built on the dominant degree in both minor and major keys. Since the ninth formed is major in major keys and minor in minor keys, these chords are called major dominant ninths and minor dominant ninths.
The I–V–vi–IV progression is a common chord progression popular across several genres of music. It involves the I, V, vi, and IV chords of any particular musical scale. For example, in the key of C major, this progression would be: C–G–Am–F. Rotations include: I–V–vi–IV : C–G–Am–F.
The major 6/9 chord is a major triad with added sixth and ninth notes. Therefore, with a root of C, the chord would contain the following notes: C, E, G (the major triad) plus A (the sixth) and D (the ninth).