The Composer brothers


If you played OoT and MM then you probably seen these two. So I have a theory to why they're poes. So poes are evil spirits that hate the world right? and when people who are bad and have done terrible things in Hyrule dies their spirit turns into poes.

So I believe that in their lifetime the composer brothers were once servants of the royal family of Hyrule that had played music for them. And then one day they had stole the Ocarina of Time from them, and they were hunted down and executed and buried into Kakariko village's graveyard. Since this was a terrible event that they had did, their spirits had turned into poes.