It is first heard in the early scenes of A New Hope during the boarding of the Tantive IV by Imperial troops, in the soundtrack piece known as "Imperial Attack". The theme is based on low sinister triplets usually played on timpani, cellos, basses and trombones. It often plays as a counterpoint to the Rebel Fanfare, during both "Imperial Attack" and "The Death Star". The motif resembles a recurring motif in Gustav Holst's "Mars, the Bringer of War."
The Imperial motif is considered by some to be an early musical theme for Darth Vader, although another short motif also appears in A New Hope in reference to Vader, consisting of a quiet triplet melody on bassoon over minor key arpeggios played on cellos. This theme features in "Imperial Attack" prior to Princess Leia's first confrontation with Vader and during R2-D2's boarding of an escape pod. It is next heard during the scene in Obi-Wan Kenobi's home on Tatooine, sounding quietly on solo clarinet as Obi-Wan explains the history of Darth Vader to Luke Skywalker ("Tales Of A Jedi Knight"). It also accompanies scenes of stormtroopers in Mos Eisley ("Imperial Cruiser Pursuit") and on the Death Star ("The Stormtroopers", "The Trash Compactor", "Chasm Crossfire"). Both the Imperial motif and the Darth Vader motif were superseded by the "Imperial March" in the following film, The Empire Strikes Back.
A new version of the motif is played in the track "It's a Trap!" of Star Wars Rebels: Spark of Rebellion, when the Spectres rebel cell infiltrates an Imperial Star Destroyer's with the Ghost to rescue Ezra Bridger. It is also played in "Gathering Forces" as part of the "Imperial Inquisition" track.
The Imperial motif briefly appears in Rogue One: A Star Wars Story, in a scene chronologically occurring immediately prior to the aforementioned boarding of Tantive IV, as a musical foreshadowing of A New Hope ("Hope"). The theme is present briefly in Solo: A Star Wars Story during the train heist, when the range troopers arrive.
The Imperial motif is used to represent the new stormtroopers in the Star Wars: The Bad Batch episode "War-Mantle."