Tritone substitution: E7 can be replaced by A#7 (a tritone away). Both chords share the same tritone between the 3rd and 7th, resolving to the same tonic.
The major 3rd and minor 7th form a dominant core, while the major 9th adds a diatonic extension. The dominant tritone preserves directed tension toward resolution.
Application
V9–I in jazz
Funk and soul
Blues harmony
Voicing & structure
Root position
v1E(E4)Bass
root
v2G#(G#4)M3from E
v3B(B4)m3from G#
v4D(D5)m3from B
v5F#(F#5)M3from D
Harmony
Compatible scales
All chord tones are contained in these scales — use them for improvisation.