Is there a way for me to find the individual files for the in-game music? I want easy access to them for something I want to try to make, and don't want to sit through so much of a level waiting for the right moment.
You can use Gildorf's UE Viewer on the game's PAK file. I'll let you figure out where the sound files are on your own (it's clearly labelled anyway). At a certain point it will ask you about the Unreal Engine version used for the game. On Windows at least you can find this out by checking out the game executable's Properties under the Details tab (currently, it seems to be 4.20.3, but that can change).
Many of the music tracks are layered and you'll need something like Audacity to merge multiple tracks into one to get something you'll actually hear in-game.
I'm not entirely sure what you're trying to make, but do keep in mind of the copyright laws and EULA involved here, especially if it's something you'll release to the public.