I can’t believe that in all my years of viewing the film hundreds of times, I never picked up on this . Turns out Vader had a theme before the Imperial March that was a lot more subdued in the original film . The video they link to near the bottom of the page really makes one aware of it . Now I will never be able to not notice it on future viewings !..http://episodenothing.blogspot.com/2016/09/the-music-of-star-wars-that-we-never_16.html
By the winged devils of Onderon! I KNOW that piece of music, could hum it… but my brain never thought of it as a THEME/MOTIF in that way. It’s overshadowed in my brain box by the more dynamic Imperial March, which is strengthened by being in multiple films.
It’s a very low-key motif. More fitted to represent a bureaucracy than a regime of terror. Hardly surprising that John Williams thought better of it in subsequent films.