This guide is for people who want to change the music theme in the game without removing (replacing) the original music theme, so they can always revert back to the old, original music.
Heroes 5 Music files and how you can create .ogg file
Heroes 5 use music files in the format ".ogg”, the problem is that files in this format are not very popular, so you need create your oun ".ogg” file first, how?
You need just a .ogg converter, like this stuff , it convert ".mp3” files to ".ogg”.
Try to convert this mp3 file to ".ogg”.
Creating directory
Now go to your Heroes 5 directory, and open the “music” folder, and create new folder in it with costom name (your choice about name).
Open the new folder and copy your new ".ogg” music file.
Lets use the name “Robot” for our new dir, after this our new music, will be in:
"*Your mine Heroes 5 directory*/music**/Robot/The_Robot_Army.ogg"**
Editing data
Now go to your data folder (data, or dataa1), and go in:
/Sounds/_(Music)/
if you want to change music of the Campaigns, heroes, terrain, AI themes (the loadings black screens), battle themes, the creadits, dwellings, grail, lose or winn battle and capaign, main menu, and towns.
(all files for that are in are in different folders, but you can easy see the names right? 
)
Lets change the music in the Maine Menu in HOF, open the “dataa1.pak” file, go to sounds "/Sounds/_(Music)/MainMenu/" and open the “a1-MainMenu.xdb” file, you’ll see this:
The most important for our work here is “Line 3”, we need just to replace the link to the original “heroes 5 main menu theme” directory with our own new folder link:
/music/Robot/The_Robot_Army.ogg”
after the editing the file will look like:
Now save the changes and everything is OK.
