C Augmented add sharp ninth

The augmented add ♯9 sonority combines two strong colors: the raised fifth of an augmented triad and the altered upper tension of a sharp ninth. The result is bright, unstable, and expressive, with a modern harmonic edge that can sound both dominant and chromatically floating. In symbols you may see forms like C+add♯9 or Caug(add♯9).

Construction

Start from an augmented triad: 1-3-♯5. Then add the sharp ninth above the root: ♯9. In C this can be voiced as C-E-G♯-D♯. Because multiple altered tones are present, spacing is crucial: if all notes sit too close, the chord can become harsh rather than musical.

Usage

Use this chord when you want intense harmonic color without fully committing to a classic altered dominant stack. It works in fusion, cinematic harmony, modern jazz, and advanced pop writing where tension is part of the character. It can also function as a passing sonority between more stable dominant or tonic structures.