The augmented add ♯9 sonority combines two intense colors: the unstable lift of ♯5 and the upper-edge friction of ♯9. It can feel dominant-adjacent, chromatic, or deliberately ambiguous depending on context. In notation, you may encounter forms like C+add♯9 or Caug(add♯9).
Construction
Build an augmented triad first: 1-3-♯5. Then add ♯9 above the root, yielding a pitch set such as C-E-G♯-D♯. Because these tones are close in color intensity, spacing strategy is crucial to keep the voicing expressive rather than brittle.
Usage
Use this chord for heightened chromatic color where a conventional dominant does not feel vivid enough. It works well in fusion, modern jazz reharmonization, cinematic cue writing, and advanced pop bridges where tension should feel vivid and slightly unstable.
Examples
- Fusion passages - chromatic dominant color before a pivot or resolution
- Film harmony - bright unstable sonority in suspense movement
- Modern songwriting - tension chord in bridge or pre-climax
Play
Keep a clear core shape and place ♯9 in a register where it sings rather than clashes. Avoid stacking altered tones in tight middle-register clusters. Resolve either ♯5 or ♯9 by semitone to make the harmonic motion feel deliberate and controlled.
Ear-training cues
Compared with ordinary augmented chords, add ♯9 sounds sharper and more vocal in the top color. Compared with altered dominants, it can feel less function-bound and more color-forward. Listen for brightness plus instability, not just dissonance.
