Award-winning pop star Pete Bancroft is at home trying to compose a new song but failing. As he listens to his past triumphs from a recording, his daughter Justine comes in and practices the song she's working on it. She asks him to help her with the song, one about her love for him, but Bancroft all but ignores her. His manager Tony arrives and warns him that the company isn't going to pay him the top salary in the business. Bancroft tells Justine to stop playing and then tells Tony to get the recording company to meet his demands or he'll quit. Tony promises to do what he can and compliments Justine on her song as he leaves. Bancroft continue to ignore Justine until she pushes him, and then he accuses her of sounding like her mother, his ex-wife. Angry, Justine walks away.
A man, Wilson Farber, calls Bancroft on his private number and offers to give him an instrument that no one has ever seen, one that will make the musician even more famous. He gives Bancroft his address and then hangs upâ€¦ and turns to a corpse on a gurney and says he's found someone better.
Bancroft goes to see Farber, who keeps a room filled with stuffed animals and a bizarre electronic instrument similar to a piano. Bancroft dismisses it as a fancy synthe until Farber tells him to concentrate on his music. The musician thinks for a momentâ€¦ and the synthe starts playing his song, exactly the way he hears it in his mind. Bancroft is willing to give anything for it, but Farber says that he only needs to take it with him and make sure he's satisfied with it. Bancroft quickly agrees.
Back at his studio, Bancroft ignores Justine and uses the synthe to compose his perfect song. He dozes off and wakes up only to discover Justine using the synthe to perfectly recreate her song. She's amazed but Bancroft claims it's merely a toy and says he has to leave. He ushers her out after having her promise not to use the synthe again.
That night, Justine sleeps while Justine concentrates on the synthe. It plays Bancroft's song on his own but then switches to Justine's music. Farber realizes that Justine is one he has to have.
Later, Bancroft brings Tony in to hear his new music. Tony recognizes Farber as the former manager of a heavy metal band. The band's lead musician died during a ritualistic on-stage performance. Bancroft doesn't believe it means anything, but is upset to discover that the synthe and Justine are both gone.
Bancroft goes to Farber's apartment and finds Justine, unconscious. Farber tells him that the device was intended for him, but now it has selected Justine. He warns Bancroft that if he tries to wake Justine up, she'll die. Farber boasts that he plans to capture the perfect song, Justine, inside of his synthe. To do so, he'll have to drain her soul. When Bancroft used the synthe, Farber realized that he was a hack with no soul.
Bancroft leaps forward and smashes his hand into the center of the machine. He only burns his own hand to the bone and staggers back. As Farber shoves him away and goes to Justine, performing an incantation, Bancroft concentrates on his own inferior song. The two songs, his and Justine, merge, overloading the synthe. As it starts to explode, Farber runs to his creation and tries to stop it. It explodes, killing him and blasting Bancroft and his daughter out of the room. Justine stares at her father's shattered hand in horror but he insists that she's the only thing that matters and she'll be his music now.