F sharp Dominant ninth sharp fifth

The dominant 9♯5 chord replaces the perfect fifth with an augmented fifth, creating a brighter, more unstable dominant color while keeping the ninth extension. It is related to the augmented triad’s “lifting” quality, but the presence of ♭7 and 9 keeps the sound anchored in dominant function rather than floating away as a pure augmented sonority often does.

Construction

Practical formula: 1-3-♯5-♭7-9. In C9♯5, a common working set is C-E-G♯-B♭-D. The augmented fifth wants to resolve melodically, often outward by semitone or along the voice leading of the next chord’s third and seventh.

Usage

Useful in jazz, blues-rock, fusion, and soul-jazz when a dominant needs extra lift and edge. It can also appear as a chromatic passing dominant color between more stable voicings.

Examples

• Altered dominant substitutions in turnaround harmony
• Blues-influenced dominant bars with brighter altered upper structure
• Fusion riffs where the ♯5 is part of the melodic identity

Play

Keep 3-♭7 clear, voice ♯5 so it does not collapse into the third in close position, and treat the ninth as the width element above the seventh. If the chord sounds too sharp, widen spacing before removing extensions.

Ear-training cues

Hear the widened fifth against the dominant seventh frame: brighter than 9, more restless than 9♭13.