My world contains a race of creature that does not speak to communicate, they sing.
They are humanoids, living in similar conditions as humans. They are intelligent, they have a complex langage, they can cast magic with their voice.
The song have to be a very particular sound that can be sweet or pretty loud. Not only a voice, but several sounds making a beautiful melody that can not be confused with anything else. For comparison I have a church organ in mind for the "song", but I don't know whether it's possible coming from a single humanoid. I have to make one of them mute in the story, what leads to the question :
What kind of organ (tongue, lungs, vocal cords, something totally new...?) does a creature needs to perform such a song ?