What you're refering to would be the ability to customize your music. In your EQ2 folder is a folder called Music. Inside this folder resides the music you hear in the game (i.e. zone music, combat music, and theme music). By creating a folder called Custom_Music you can have custom music for those. I'll give you an example of how to create a custom song for roaming through Antonica:
In the EQ2 folder, create the folder called Custom_Music.
Inside the Custom_Music folder create another folder called zones.
Find your favorite mp3 file (let's pretend we use BornToBeWild.mp3).
Copy the BornToBeWild.mp3 into the zones folder.
Rename the BornToBeWild.mp3 to antonica.mp3 (exactly as it is in the Music > Zones folder - it is case sensitive).
Load your game and run through Antonica shouting "BORN TO BE WIIIIILD!!!"
And you can do the same for the other folders. I myself use the Mortal Kombat theme for all my combat music. On a side note, there's a folder called XMI. XMI from what I understand is some kind of metadata and I wouldn't bother that folder unless you know what you're doing.
As far as in game sounds like swords clashing and people talking, to my knowledge there's no way to change these at the moment.
Hope this clarifies a few things