well much as compiling a music mod is a nice idea,i havnt the faintest idea how to do that!
All that you need to do is find the music that you think would draw the person into the time period of the mod, and once you do have the music selected, just rename the .mp3's to what you like them to replace in the game.
SOWGB_Intro.mp3 of course is the intro music when you start the game.
SOWGB_End.mp3 is the Battle Report music
SOWGB_Multiplayer.mp3 is the Multiplayer menu music.
Okay two ways to get that last pickle out of the pickle jar...
Once you choose the mp3's you want to use in the game all that is then needed to do is rename which .mp3 you have chosen to the above names, then copy them over to your <drive letter>:\NorbSoftDev\Scourge of War - Gettysburg\Base\Music
NOTE: Make a backup of the music directory first before overwriting the music files.
OR...
Go to the mods directory in Scourge of War - Gettysburg. Create a directory called whatever suits you to name it, for me I would name it New Music. Once I do that go into that directory, and create one more directory called "Music". Once you do that you just copy those music files you wish to use into that directory you just made.
Now you just go into the game, select the mod New Music, and activate it (yellow bar to the left of the mod should be showing). If your music is not playing right away, just restart the game.
I just tested this before I wrote it, and it works fine.
