The possibilities for altering Dominant 9th chords are numerous. That means that the number of upper extension chords are numerous since altering a note in the chord creates a different upper extension chord. There are eight possibilities (see sidebar). The alterable notes in a Dominant 9th chord are the 5th and the 9th. They can be raised or lowered singly or in combinations.
First Single Alteration: Dominant Flat 9
The main thing to realize about dominant flat 9 chords is that the extended chord is a full-diminished seventh. The inversions of C7(b9) with the root omitted are full-diminished 7 chords running in minor thirds, based on the third, fifth, seventh, and flat ninth of the chord.
So diminished scales and arpeggios are the things to use in this context.
Here is a diminished phrase for C7(b9). I visualize it based on the third of the chord so it can be thought of as a Edim7 over C.
Notice that in the Key of Bb, open strings are involved. Most players will finger the phrase differently because you don't have to fret an open string. I prefer to finger it the same way as the other keys. I finger the open string as if it wasn't open. It's not that one way is right and the other is wrong, either way will work. This issue is an illustration why you should practice everything in every key. Certain keys have problems that other keys don't have. Thinking through those problems and solving them is an invaluable part of the process of mastering the instrument.
Since diminished patterns are symmetrical, the same fingering can be applied to the seventh of C7(b9), which is Bb diminished 7.
II - V - I Examples
The diminished pattern is visualized from the 7th of the G (F).
Example 2:
On the G7(b9) chord, the diminished phrase is visualized from the third of the G (B).
