Drawing from a variety of sources, Music of the Ages - Norse Edition changes nearly every music track in the game to Norse-themed ones. Great care was taken to ensure that the new tracks don't feel out of place or radically different from the old, so as to not disrupt the feel of the game. Great for anyone who plays Norse all the time, is currently going through the Norse section of the Fall of the Trident campaign, or just enjoys classical Nordic music in general. As far as I can tell, this mod is safe for multiplayer; I playtested it online several times without issue.
Installation: If installing for Age of Mythology Extended Edition (Steam):
Drag the "Music of the Ages - Norse" folder into the Mods folder in your AoM directory, then launch the game and activate it from the mod manager.
Default Steam directory: C:/Program Files/Steam/steamapps/common/Age of Mythology)
If installing for a disc-based copy of AoM:
Make sure to make backups of the original music files in case you want to uninstall later.
Then, simply extract the "sound" folder into your Age of Mythology installation directory and overwrite everything when asked.
Default Disc directory: C:/Program Files/Microsoft Games/Age of Mythology
Uninstallation: Age of Mythology Extended Edition (Steam):
Just go to your mods folder and delete "Music of the Ages - Norse".
Replace the modded music with your back-ups. Otherwise, you may need to repair the installation with the disc.