FamousThe Empire Strikes Back1980 · John Williams
Two chords at once: E♭ minor over G minor
The Imperial March's own harmony (G minor against E♭ minor) stacked into one chord; Lehman lists it as a stand-alone 'leitharmony' in every film, especially Return of the Jedi and Revenge of the Sith
Two minor chords stacked a major third apart, E♭ minor on top of G minor, sharing only the note B♭. It freezes the Imperial March's signature move, G minor sliding to E♭ minor, into one chord, so the villain's harmony can be heard without his tune. The half-step clashes, D against E♭ and G against G♭, give it its cold, menacing colour.
Also called Imperial, Imperial March polychord, E♭ minor over G minor
Sources: Frank Lehman, Complete Catalogue of the Musical Themes of Star Wars (updated 19 June 2023), theme 10b-g (Imperial March continued), 10g 'Polychord' · Mark Richards, 'John Williams Themes, Part 3 of 6: The Imperial March', Film Music Notes