No easy way out, huh? Dang. Well thank you for your time in any case.

I did however do a little digging. Looks like there still might be a glimmer of hope. Now I've managed to convert my custom music into .wem and I'm able to go through the soundtracks after I convert the official ones into .ogg format. My only problem is to find the files that would be responsible for starting each track.

If it's impossible to add extra "lines" for new tracks, I guess my only chance would be to edit the original soundtrack files by adding the new music tracks into the old ones with a little pause between each other and then repack them as .wem

So this is what I've done so far, in case anybody's interested:

Tools used

ww2ogg

revorb

Audacity

Wwise

Converting your own music to format ES2 understands

1. Get some music, skip step 2. if your files are already .wav

2. Open up Audacity

-> open up your music file

-> hit file - export audio

-> now you have .wav files

3. Open up Wwise

-> start a new project, give any name

-> hit project - import audio files

-> hit add files - get your .wavs - hit import

-> hit project - convert all audio files

-> now you have .wem files

4. Replace any music files in Endless Space 2/Public/Audio/soundbanks/

-> use the exact filename in ES2 folders

Using those steps you can simply replace any music you'd like. But that's not what I'm after so I tinkered a bit more.

Converting ES2 music into playable format

1. Create a new folder

-> move ww2ogg & revorb, all their files to this folder (including the extracted ww2ogg.zip)

2. Dump all the ES2 .wem files into this same folder

3. Create a text file

-> type this within the file

for %%f in (*.wem) do ww2ogg.exe %%f --pcb packed_codebooks_aoTuV_603.bin

pause

for %%f in (*.ogg) do revorb.exe %%f

pause

-> the pause text is optional but I'm a noob and copypaste ftw

-> hit file - save as - nameofyourchoice.bat - be sure to select file type as all files

4. Run the nameofyourchoice.bat

-> wait and hit enter for the two times it'll stop, this might take a minute

-> you now have .ogg files

5. Open up the .ogg files with your media player of choice

-> some files were mute with WMP & VLC when I tried

-> Audacity opens up all files from what I tried

So at this stage I can open up the .ogg files and browse through the music files. I might add a list of the tracks here another day when I've time to go through them all for a convenient list. Right now I'm looking at a random bunch of numbers as filenames but I think the largest files are the music tracks. At least the first few were.

Now if there's really no way to add new tracks to the game, one could open up the .ogg files with any audio tool and simply add your own tracks to the end which is what I'm thinking I have to do. I'm just worried the quality of the sound will go down with multiple file type conversions.

Sources

http://nmsmodding.wikia.com/wiki/Replacing_Audio

https://www.reddit.com/r/killingfloor/comments/35d5w6/how_to_extract_game_audio_files_guide/

https://www.youtube.com/watch?v=g-aYS_3enro