upvote ALL the things
The somewhat exotic oriental feel of the Atreides, the Industrial-like epic rock of the awesomely cruel Harkonnen, The batshit crazy electronic music of the cold, calculating, machine-like Ordos.
Nod Crush, Valves, Pharotek. Do I need to say more?
Entire soundtrack is ingenius and makes the game so much better. Amazing chemistry between music and the game itself.
Each theme is so great and add to the feeling of exploration, faction-territorial themes change slightly when you are safe or about to get attacked, or in a real battle. BUT the main theme remains similar and the change is seemless, giving you lots of immersion.
Hats off to Kirill Pokrovsky, and Frank Klepacki, and many others.