The dominant 9♭5 chord keeps the ninth extension while replacing the perfect fifth with a lowered fifth. That creates a leaner, more angular dominant color: the ninth still supplies melodic width, but the chord’s interior tension shifts toward the tritone family in a way that feels sharper than a plain 9 chord. It is common in jazz, fusion, and blues-influenced harmony when you want dominant function with a more modern edge.
Construction
Practical formula: 1-3-♭5-♭7-9. In C9♭5, a common working set is C-E-G♭-B♭-D. The fifth may be omitted in some voicings, but the lowered fifth is the defining alteration when the symbol is explicit.
Usage
Use it on dominant stations where you want altered crunch without necessarily adding ♭9 or ♯9. It works well in turnarounds, secondary dominants, and chromatic dominant approaches where voice leading benefits from semitone motion around the altered fifth region.
Examples
- Jazz comping on V chords that need a brighter altered interior than 7♭9
- Fusion riffs that emphasize the ♭5 as a melodic color tone
- Blues-jazz hybrids where the ninth is in the melody but the harmony wants more bite
Play
Keep 3-♭7 clear, voice ♭5 so it does not collapse into the third in very close position, and let the ninth sit above the seventh for width. If the chord sounds too sharp, widen spacing before removing the ninth.
Harmonic function in progressions
It still behaves like dominant harmony preparing a target, but the ♭5 pushes the ear toward more chromatic resolutions—often landing nicely when the next chord simplifies the texture.
Ear-training cues
Hear ninth width combined with an altered fifth interior: more angular than 9, less “stacked altered” than 9♯11♭13.
