Guild Wars 2

Is it possible to put my own music to play in-game instead of the original soundtrack. For example, could I set a different song to play while I’m in combat or in a dungeon, or even better, could I change the “Defeated” song to something else.

Yes you can create custom playlists for certain circumstances (battles, bossbattles, ambient, night for example). I’m on my phone right now so I can’t give you a link but the wiki/google should have a guide for that; it’s pretty simple anyway. Iirc you can’t change the defeated soundtrack though, not that you want to hear that one often. :p