Well there is a music text file in
C:\Program Files (x86)\Steam\steamapps\common\MountBlade Warband\Modules\Napoleonic Wars
The tracks look like this william_boyce_sinfonia_1.mp3 268704768 268704768
You could probally edit in new music but i dont know what the 268704768 268704768 means at the end. It looks like those numbers are used for every track so im guessing that if you put for example song_1.mp3 in the music folder then add the line song_1.mp3 268704768 268704768 to music.txt it will probally play. I've never tried though and I'm just guessing.
This is a bit complicated, and unnecessary. All you need to do is take the MM music file from the MM music folder and move it into the NW music folder then rename that MM file to be the same as one of the existing music files.
Say you want to add MM's "music1.ogg" file into NW. You would go into MM's music folder, find the file, then copy and paste it into NW's music folder. Once you've done this, you rename "music1.ogg" to one of the files there, for example, "bach_cello_suite_1.ogg". Then, when Bach's Cello Suite plays, you will hear Music 1.
Yep, and make sure you replace the spaces with _'s, because it won't accept them otherwise. Regarding the numbers at the end, the 268704768 268704768 just tells it to play while in a game server. There's another set of numbers to indicate which track should be the main menu music. Also, you need to change the number at the top of the .txt file to however many songs are in the .txt file after you import them
This is my music FOLDER.
This is my music .txt file (Don't worry if your .txt interface looks different than mine, I'm using notepad++, which I recommend to everyone)
As you can see, there are 45 lines, -1 because of the actual # at the top, so that makes 44 songs. The thing called cant_find_this.ogg is necessary for all .txt files regardless of what music you have in there. My music file is filled with mostly custom music.