D7#9 holds the major 3rd and in the same dominant chord: D, F#, A, C and E#. The two notes sound a semitone apart.
The major 3rd stays essential. In blues, 7♯9 can stand on the tonic itself as well as lead to another chord.
Also written D7(#9), D7+9 or D7♯9.
Drop the third voice from the top an octave instead. The wider gap skips a string, so the muted string is part of the shape.
That result, 3–R–5–7, is the shape usually meant by drop 3. Named by its bass note, as the inversions are here, it is the 1st inversion.
More familiar jazz shapes are drop 3 than drop 2.
D7#9 can replace a plain seventh chord wherever a bluesy sound is wanted, even as the first chord of a tune, where other altered dominants don’t belong. It sounds like home, with no urge to fall a fifth.
Listen for: The sharp nine, a minor third sounding over the major third, holds through the IV7 as its flat seventh.
Like the other altered dominants, D7#9 works in front of a chord a fourth higher, such as Gmaj7, a chord a half step lower, or a minor chord on its own root.
Contains D7#9 and adds flat ninth, sharp eleventh and thirteenth.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.