@spiritovod: Ah yeah, I think I fiddled around with it in HxD to get only the MOGG data working but ended up messing it up completely...
But I don't even know how usual mogg looks like
A quick Google search for "Download MOGG Files" brought up some blogspot website that had links to 2 MEGA folders - here's one of the files so you can have a look at an MOGG file
they even implemented drm by denuvo devs for audio subsystem
Into the .uexp files?
Someone's managed to get an unpacked executable (probably just with Steamless at first glance at the filesize difference) in case that would be helpful.
I've already posted it in the Discord I've created to better keep track of it, but I feel the best approach for this would be the following:
Perhaps the better thing to look into would be making a custom song loader entirely.
Scan a specific folder with subfolders (e.g. "CustomSongs") - put a specific file in each one (song.ini or whatever) that contains the info and then have it call specific methods in the game itself so it links those ingame.
I wouldn't be surprised if there were methods to load raw audio files - surely the devs must be testing with that, too