Modding the music for RTW 1.5/BI 1.6 is still a fairly simple process. To start off, put the mp3 files you want to use into the bi\data\sounds\music folder. If you don't have a music folder in the sounds directory, just create a new folder.
Next, you need to modify the descr_sounds_music.txt file in the bi\data\ folder, but first, rename the original descr_sounds_music.txt to something like ORIGINAL-descr_sounds_music.txt this will ensure that you keep a base copy of it for reference or a backup. The structure for this file is pretty straight forward, but I'll explain a few things. Quote:
state MUSIC_BATTLE_BATTLE
event
folder data/sounds/music
Battle1-Imperial_Conflict.mp3
Battle2-Mayhem.mp3
Battle3-Melee_Cafe.mp3
Battle4-Romantic_Battle.mp3
end
This section covers the music for the battle map, which is clearly marked. The "state MUSIC_BATTLE_BATTLE" restricts this music loop to the point where one or more of your units is engaged in combat with another unit. There are also the BATTLE_TENSION and BATTLE_MOBILIZE sections. The first playing while all of your units are in a state of rest and not moving, while the second plays when a move order is given.
It's important to note that these music selections are all based on culture type. So, if you change it for the romans, it will only affect the Western Roman Empire, Eastern Roman Empire, Western Rebels, and Eastern Rebels. You will have to change the loops for each culture type if you want different music for the barbarians or eastern factions.
To change the music, all you do is replace the Battle1-Imperial_Conflict.mp3 lines like I have in my example: Quote:
state MUSIC_BATTLE_BATTLE
event
folder data/sounds/music
big_battle.mp3
end
Now when one of my units engages in combat, the game loops big_battle.mp3 untill a different state is triggered.
After modifying the .txt, make sure that you save your changes.
The final, and most important for 1.5/1.6, is forcing the game to generate a new events.idx file. To do this, go into the bi\data\sounds folder, and rename events.idx to ORIGINAL-events.idx
The next time you start up RTW/BI, the game will generate a new events.idx file based off your modified descr_sounds_music.txt file. I would recommend trying a custom battle to see if your changes worked.
If there's anything that needs clarifying in these instructions, feel free to ask me for help.