For anyone who have this doubt: 1-You have to convert the song to ogg(Using VLC Media Player or audacity as ITurkishmapping said) 2-Go to the music directory of the game 3-Search an archive called Age_of_Civilizations 4-Change its name to Age_of_Civilizations.txt 5-Open it and add the name of your song  6-Add an ; at the end.Example:random music.ogg;Your song.ogg; 7-Close the text and save it 8-Move your song to the music folder 9-Rename the Age_of_Civilizations.txt to Age_of_C