Below is a list of all the major characters, settings/locations, and ideas and their "theme songs" that represent them, or at least what I listened to a lot while I conceived the ideas for who/what they are.
Some of these songs (Raine, I'm looking at you) won't make sense unless you take them in the context of all of the books as a whole, once you read them.
Characters who appear across multiple books may have different songs as they grow and change over the course of the series.
Click each character/pairing/etc. to expand the embedded song.
In chronological order of release/anticipated release:
2. Venus and Lysander
This book's major inspiration
Lord Commander Valerie of Lysander
Lady Chancellor Lucrezia of Azrith
Emperor Xavier of Tenrose + The Empire of Tynan
Queen Beatrys of Tenrose + The Kingdom of Tibor
The Port City of Indra
Elysia's show of absolute power in Indra
The Edge of Reason
Elysium the Underworld
Hatred of sorceresses
Enabling Val's tyranny