Singer in the snow

On Nevya--a sunless world whose population is sustained by the heat and light its Cantors and Cantrixes create from psi energy channeled through music--Emle, a young Singer who cannot channel her psi, is sent to a remote outpost as a translator for a voiceless Cantrix, where, struggling to come to terms with her flaw, she gets involved in the life of a troubled, talented girl being exploited by her abusive stepfather.