The musical score for Star Wars: Republic Commando was created by Jesse Harlin, who served as a music editor and composer at LucasArts. This soundtrack was initially offered as a complimentary download on the game's official webpage, but it was removed when LucasArts shut down the site. Departing from the conventional Star Wars sound, the music adopted a fast-paced, intense, and vocally-driven style, introducing several original themes and motifs specific to the Republic Commando game. The newly introduced clone military theme incorporated a minor third motif derived from The Emperor's Theme, complemented by lyrics in the ancient Mandalorian tongue, a language conceived by Jesse Harlin. This marked the debut of Mando'a, which was subsequently expanded into a fully functional language by Karen Traviss.
In addition to the original compositions, the game's music also incorporated themes by John Williams, most prominently the Droid Invasion Theme, alongside reworked versions of Williams' compositions. As an example, the concluding mission on Kashyyyk showcased a modified rendition of the Escape from Naboo theme, featuring a prominent male choir (also a common element in the original soundtrack). Furthermore, the turbolift scene in the Prosecutor contained a brief piano remix of The Imperial March as a hidden easter egg.