Wow this is quite hard for me, but the funny thing is I can think of singular music for different scenes of not only the novel in writing right now but also of the ones I wish to write in true future! A general one however, it's more difficult, it should be one that encompasses the main aspects of the novel... Hmm... Well, I will go for the one I feel that defines it the most: https://youtu.be/OTRi_G8eew4
"No limits exist" is my philosophy for writing so for my first official novel and with its thematic of sci-fi and the former, I think is quite fitting! 
https://m.tapas.io/series/The-Devils-Touch (time to take the chance and self-promote! :evilgrin:)