This role is the grand narrator of the story, the background voice describing each text block that isn't said by a character. Our DM in real life is a male, but I am open to ANY male or female sultry voice if it hits right. Think of a DM at a tabletop RPG game trying to sound imposing and wise, omnipotent but not in an annoying or funny way. The videogame Baldur's Gate 3 has a good example of a DM describing what the character does and sees, and that's a female narrator. For males, I like a Ron Perlman style narration. This is one of the only times they are directly talking to the Player and setting the scene.