Eternal Sonata

Eternal Sonata follows general conventions of the role-playing genre; the player controls a party of up to twelve characters to explore the world, interact with its inhabitants, buy and sell equipment at shops, and encounter monsters while in the field. These encounters are visible and the player can choose to avoid the encounter, if possible, as well as gain the advantage in battle by approaching them from behind. Experience points are awarded to all members of the party, though at a reduced rate for those not involved in combat, and characters improve in various statistics and learn special combat skills as they level up. Weapons, armor, and accessories can be used to improve these statistics, which can be purchased through money earned in combat, found in chests, or by selling equipment and photographs which Beat can take during battle.

The player can also find Score Pieces scattered about the world, which represent short musical phrases. Various NPCs in the game will offer to perform with the party, requiring the player to match a Score Piece to the phrase they offer, with the resulting composition being ranked. Discordant matches will result in no reward, but close or perfect matches will gain a bonus item from the NPC.

The game takes place mainly within Chopin's dream world, with brief segments in the real world where he is on his deathbed. The story is divided into eight chapters, each represented by one of Chopin's compositions and related to events in his life. The dream sequences combine the game's fictional narrative with elements drawn from Chopin's biography and musical works.

Chopin meets Polka, a young girl who possesses magic and will soon die from her illness. She also sells floral powder, but her business is being threatened by the introduction of the cheaper mineral powder, which is mined by Forte's ruler, Count Waltz. After being shunned by the citizens of Ritardando, who believe that her magic is related to her illness, she decides that she wants to do something with her life before she dies. The party sets out to meet with Count Waltz regarding the mineral powder and to stop the mining of Mt.

Director Hiroya Hatsushiba stated:

People who play games and people who love classical music are not necessarily sharing [the] same type of interests. Most people in Japan know the name of [Frederic] Chopin; however, most of the people who know of Chopin think he is just some kind of a great music composer without knowing any more about him. Most of them have heard Chopin's music but not a lot could put his name to it immediately. By creating a colorful fantasy world in Chopin's dream, I was hoping that people would get into this game easily and also come to know how great Chopin's music is.

Famitsu rated the game 9/9/9/8, for a total score of 35/40.

During its release week, the Xbox 360 version the game reached second place on the Japanese sales charts at 49,334 copies. The following week, it had dropped to 35th. The PlayStation 3 version debuted on Japanese sales charts at number four with around 34,000 copies sold. Famitsu reported that year-end Japanese sales of the game reached about 70,435 copies on the Xbox 360 in 2007 and 53,314 copies on the PlayStation 3 in 2008.