Writing in silence has never really worked for me.
The Seventh Empire has always been cinematic, in my head. I see scenes (especially action scenes) like it's a movie playing just for me. And what would an action movie be without an epic soundtrack?
When we started working on the first book, Sam burned me a CD. Doesn't that make me sound old? Ha! It was all this really incredible Asian-inspired music. He labeled it "Asian Coolness." =D I think I still have it somewhere, even though I no longer own a CD player. I played that CD every time I sat down to work on the book, and it really set the tone for the Seventh Empire.
For book 2, Sam created "Asian Coolness vol. 2" which I loved, however, most of the tracks were pretty chill. When it came time to write the climax of "Buk Tu" and the humongous battle therein, I needed something a bit more intense. I ended up getting hooked on the album "This Is War" by Thirty Seconds to Mars. I wrote the Mount Tandashin sequence in a single, overnight session - approximately 12,000 words in about 10 hours - listening to that album on repeat. Listening to "Vox Populi" still reminds me of that night!
Book Three has obviously been a long time in progress, and I've gone through several iterations of the "soundtrack." However, for the past year and a half, I've relied on a set of tracks I found on YouTube. Writing, revising, editing, and proofreading have all been accompanied by the playlist I affectionally dubbed "EPICNESS." The first three videos in particular have been repeated many, many, many times as I've worked on "Buk Tri."
Perhaps when the time comes, you can read "The Seventh Guardian" with this music playing in the background - then your soundtrack will match the one to which it was written.