A Dominant 7th Sharp 9
A7#9 · Root
Every chord tone stacked from the root up.
Click keys to experiment with the chord
A – C♯ – E – G – B♯
1 – 3 – 5 – b7 – #9
The sharp ninth adds blues-inflected tension to a dominant seventh, often heard on a tonicized V chord. It fits the altered scale or the half-whole diminished scale; the 3rd and b7 resolve by fifth-root motion.