Tritone substitution: Gb7 can be replaced by C7 (a tritone away). Both chords share the same tritone between the 3rd and 7th, resolving to the same tonic.
The minor 9th forms a compound-semitone dissonance with the root, while the minor 7th preserves dominant function. On V in minor, b9 normally corresponds to scale degree 6 and resolves downward.
Application
V7b9 → i in minor
Flamenco and Latin jazz
Minor jazz cadences
Voicing & structure
Root position
v1Gb(Gb4)Bass
root
v2Bb(Bb4)M3from Gb
v3Db(Db5)m3from Bb
v4Fb(Fb5)m3from Db
v5G(G5)m3from Fb
Harmony
Compatible scales
All chord tones are contained in these scales — use them for improvisation.