The hero of Eternal Sonata is a real historical character, the famous 19-century Polish composer Frédéric Chopin. The game begins with Chopin lying on his deathbed and having a strange dream in which he is transferred into a fantasy world where places and people have musically sounding names. Chopin encounters a girl named Polka, a magician who is on the run from her own destiny (since all magicians die young in her world). Other people join them on a quest to overthrow an evil nobleman. Events from Chopin's real life are shown as parallels to what happens in his dream.
The game is conceived in the tradition of Japanese RPGs, with a linear, character-oriented story line and graphics with animé influences. The gameplay combines several elements of classic turn-based combat, strategy, and real-time fighting. Your party has a limited amount of time for a turn, during which you can move a character over the battlefield and execute actions, which take different amount of time depending on their effects. Light plays an important role during battles, since characters have different attacks and spells when standing in the light or in a shadow.
The game uses works by Frederic Chopin as its musical score.