Hello.. As of 4.1, the admin system has changed
In 4.0 and less, you simply added the admins in a line.. like:
es_xset music_admins "steam_0:1:1234;steam_0:1:5421;steam_0:1:1515"


4.1+ Is a bit harder.. But better
As you can now add/remove admins ingame.. ( If you're Extreme Admin )

The admin file is:
../addons/eventscripts/music/es_music_db.txt

It works like this:

"music"
{
	// Steam id of the person
	"STEAM_0:1:7589873"
	{
		// Admin type:
		// 1 = *Admin
		// 2 = **Extreme Admin
		//
		// * Admins can force music, force stop, access !musicadmin and more..
		// ** Extreme Admins can do the same as admins, AND add/remove admins..
		// 
		// 
		// 
		//
		"music_type"	"2"
		// And now the name of the person..
		"music_name"	"CheeTaH"
	}
}

Can't get it working? Contact CheeTaH :)
I'll me more than happy to help you