The 7♭5 chord is a dominant 7th with a flatted fifth — containing two tritones that create maximum harmonic tension. It is used in jazz as an altered dominant, tritone substitution, and whole-tone harmony device.
Two tritones: The 7♭5 chord contains two tritones — root to ♭5 and 3rd to ♭7. This double-tritone structure makes it the most tension-filled dominant chord available. The whole-tone scale is its natural match, and bebop pianists use it extensively for colourful dominant substitutions.