Altered Dominant Chords
Altered dominants keep a dominant chord's major third and minor seventh while changing the fifth or ninth to intensify its resolution.
The Dominant Core
A dominant seventh uses R-M3-P5-m7. The M3 and m7 form a tritone that resolves strongly toward the tonic. An altered dominant preserves that functional core while changing one or more color tones.
Common Alterations
♭9 sits a half step above the root and commonly resolves downward. #9 sounds like a minor third above the root while the chord also contains its major third, producing the bluesy 7#9 color. ♭5 or #11 replaces or colors the perfect fifth with a tritone. ♭13 adds the pitch class of an augmented fifth above the dominant.
How They Resolve
Altered tones normally move by half step into notes of the destination chord. In G7♭9 resolving to C, Ab can fall to G while B rises to C and F falls to E. The altered notes add tension; the major third and minor seventh preserve the chord's dominant identity.
Try It
Compare G7, G7♭9, G7#9, G7♭5, and G7♭13, resolving each one to C. Watch which interval colors move by half step and listen for how each alteration changes the intensity without changing the destination.