Open the songs.txt ( /Hearts of Iron IV/Hearts of Iron IV/music/song.txt). Your music is technically added to the game, but now you have to define the conditions needed for your song to be played. The ID of the music file ( A New Song) can't be longer than 63 characters (the german mutated vowels like ä, ü and ö count as 2 characters) or the file will fail to load at the start of the game.
In this example we will name our file new song.ogg. In this file you'll add your music into the game. Open the music.asset ( /Hearts of Iron IV/Hearts of Iron IV/music/music.asset). You can find a lot of online converters on the internet.
Your music file should be in *.ogg format and put into the music folder of the game.
