The chord is D-flat dominant 7 It’s the same example as on the wiki page for “tritone substitution” - ‘For example, in the key of C major one can use D♭7 inste

The chord is D-flat dominant 7 It’s the same example as on the wiki page for “tritone substitution” - ‘For example, in the key of C major one can use D♭7 instead of G7.’