This is the 1980 Bookclub Edition of Songmaster. Songmaster is a 1980 science fiction novel by Orson Scott Card about a young boy with a beautiful, emotion-amplifying singing voice. Published a few years before Card's more famous Ender's Game,
In a vast future human empire, children with exceptional singing ability are secretly gathered and raised in the mysterious and isolated "Songhouse". They are molded into "Songbirds," who possess the power to magnify people's emotions through their singing, which can be used to either heal or destroy. 
 
The story focuses on one of these children, Ansset, a prodigy with the most powerful voice ever heard. His ability makes him a valuable asset and a dangerous weapon. He is taken from the Songhouse to sing for the aging Emperor Mikal, becoming a central figure in the politics of a treacherous galactic empire.