1. Gather your music files.

2. Convert them to .ogg using 3rd party tool. (e.g. FormatFactory)
( Nevermind. You can actually use .mp3 files, not sure if other formats are supported. )

1. Navigate to game directory -> music folder.
( C:\Program Files (x86)\Steam\steamapps\common\Age of Civilizations II\music )

* 2. Move "Impact_Allegretto.ogg" to somewhere safe.
( The game seems to fixed it as start theme song. )

3. Delete irrelevant songs in this folder. ( Subdirectories don't really matter. )

4. Place all your .ogg or .mp3 music here.

5. Download and place AoC2Music.exe in this folder.
( Can be download here: https://drive.google.com/file/d/1a53VV4v7tj_v9jARyjKQXlI_AkU9rfZG )

6. Run AoC2Music.exe which will replace spaces in music names with underscores then generate or replace "Age_of_Civilizations" file for you.

** 7. Move Impact_Alligator.ogg back to this folder.

==================================================================
* You have to do this unless you want to include Impact_Allegretto in your playlist..
** Your playlist will not start if there is no Impact_Allegretto.ogg present at launch..

Music Pack
Kenji Kawai - World War 2 Album (.ogg)
https://anonfile.com/P5G3y8H6na/Kenji_Kawai_-_WW2_7z

Alternative "Impact_Allegretto.ogg"
Age of Empires 2 - Wololo
https://anonfile.com/v7j4zaHene/Impact_Allegretto_ogg