The 7th with flatted 9th chord is a five note chord which adds a b9 interval to a dominant 7th chord. A b9 interval is an octave plus a minor 2nd, so we are actually adding tones from the class of intervals that is a halfstep higher than the root. Example: a G7b9 specifies a chord whose root is G and which uses pitches drawn from B (major 3rd), D (perfect 5th), F (minor 7th) and Ab (b9). Listen now to four different voicings of the F7b9 chord.