It’s not medieval music. Some of it is created by modern-day music artists, while one of them actually comes from another video game.
I present to you gameplay videos of people playing FNAF 2, which originally used a theme written by Bjorn Lynne of Team17 theme for its menu music. People would get copyright claims by YouTube and takedown notices by Bjorn Lynne just because they played the game and the menu music played. This is a real issue that I’m not just making up.