They don't really do magic, or much of it more accurately. They have the ability to sing and use that to control people to do what they want; that's where the siren inspiration comes in. They're all equally talented at this and equally resistant, one can just choose to develop the skill or resistance more (developing one sacrifices the other in equal measures). It's frowned upon to do in most communities. TL;DR: read the post its 1 paragraph bruh