What is the name of this piece of musique please?

I have been looking for the name of this song but I cannot find it. The song is sung par a girl ou woman and she goes naaaa nananananana and another one continues nanana naaaaa and is repeated. It is a very slow piece from a soundtrack but I don't know from which movie. That's all I know about it. Can toi help me out please? I'll give hommages to anyone who helps. THANKS.