A 7#9 (A7#9)
Notes in A 7#9
Inversions
Same notes as A 7#9, with a different chord tone as the lowest note. Useful for smoother movement between chords instead of jumping around the keyboard.
Root position
A in the bass
1st inversion
C# in the bass
2nd inversion
E in the bass
3rd inversion
G in the bass
4th inversion
B# in the bass
Open voicings
A close-position chord like A 7#9 can sound cluttered in the middle of the keyboard. Jazz players open it up by dropping one note down an octave, spreading the same notes wider without changing the chord.
Drop 2
G on the bottom
Drop 3
E on the bottom
Press A, C#, E, G and B# together on the keyboard and you're playing A 7#9.
A dominant seventh with a sharpened ninth on top, best known as the Hendrix chord from its heavy use in classic rock and funk. It blends major and minor color in a single chord, since the sharp ninth sits on the same key as the minor third stacked over the chord's major third.