Changing Tunes, by Donna Jo Napoli, 1998

When Eileen's dad moves out, he takes the piano with him, forcing her to practice in the school auditorium every afternoon with a janitor for her audience. But she can't bring herself to tell her best friend Stephanie why she plays at school every day, or what's really going on at home. A middle grade divorce story with disappointingly stiff characters and unremarkable events. Not recommended.