In Mark Levine's Jazz Theory Book (section about tritone substituion), he says (paraphrased):
When the tritione substitution contains the 7th in the melody, you can add a #9 to the chord.
Bb7 is replaced with a
E7#9, where the
#9 is a
G, major 3rd
Which would give you V7#9 a tritone up from the
V in a
ii - V - I.
I don't remember him talking about a mode this chord belongs to?
Is this the same as a
V7b9 using the
half-whole dim scale?
What mode best fits this chord? Assuming "best fit" is similar to playing Mixolydian on a Dominant Seventh.