You're probably having trouble with Sunken Temple because it is a WMO. It has its own music rather than inheriting the zone music. I don't know how to change this though. I tried hex edit and a notepad search and couldn't find anything related to .mp3, .ogg, or .wav in the WMO file. I imagine the music might be designated in another file but I"m not sure.
Check AreaTable.DBC (export from enUS/enGB locate.mpq)more info about this DBC here: http://www.wowdev.wiki/index.php ... aTable.dbc
You also have to edit this table. http://www.wowdev.wiki/index.php ... aTable.dbc
Yes, because it's their "parent" iRefID from AreaTable.dbc. It will be the same for all entries of this WMO. You should just look to 8 and 9 coloumns of WMOAreaTable.dbc. This way you can track the filenames.