I figured it would be fun for us to choose our characters' leitmotifs.
A leitmotifs can be a piece of music (or even a part of a greater piece of music) that represents a character, an idea, a type of event, anything really.
For example, in volume 1, something I did was use Who Will Know from Shin Godzilla as Magnes' leitmotif whenever something would involve him, black holes, or just the general existential idea of his ability when it would involve the concept of the "void": https://www.youtube.com/watch?v=CrXTS10h2WI
My final use of this was when I blatantly put it in a scene with Wasteland Magnes, as he is the Magnes who most deeply and closely associated with the Void (I intend to do a backdated solo scene between Magnes and Wasteland Magnes in the future, as it was a rather essential character point to me that I needed to do). However, in my head, this song as a leitmotif would have likely played for the final time during the possession of Eve and the death of Elaine, conceptually tying in the Entity with Magnes' concept and perception of the Void as a living thing, and thus wrapping it up as a leitmotif (which is why I intend to choose new ones in volume 2).
Komm Süsser Tod from End of Evangelion was used at the end of the fight with Virus Kazimir, because in my head it was a leitmotif for the end of young Magnes' youth and a sort of grand reflection on the culmination of his youthful mistakes. While he would come to make many more mistakes, these were for different reasons than simple inexperience and immaturity, which to me is what Komm Süsser Tod represented. https://www.youtube.com/watch?v=oIscL-Bjsq4
Also, as a general leitmotif for the travelers, I tended to use Muse's The Dark Side: https://www.youtube.com/watch?v=e0UWT0dFSQE
For volume 2 I intend to think a lot more extensively about leitmotifs and what I associate things with in specific situations. I intend to have ones for specific interactions with specific people, the idea of specific people, and all kinds of stuff.
As we're and RP and not a movie, I think the ideal approach to leitmotifs is to think of what different things would have if your character was the main character in a movie. What leitmotifs, from their perspective, would be associated with the world that they're living? How do you want to paint a picture of your character's reality?
I think this is a bit more interesting than simply making a playlist. Come up with your leitmotif songs and explain why that song applies to the idea/character/situation! I think it'll be fun. And yeah this means you can have themes that sort of represent your character's idea/relationship of other characters. Like, what would play when your character's most hated enemy enters the room?
Have fun!
addendum: Yes I am aware that full songs are generally not leitmotifs, but it's the most practical way of thinking of them for an RP.