and Dream Drop Distance, the main characters write their own journal entries. The games are influenced by their parent franchise, Final Fantasy, and carry its gameplay elements over into their own action-based, hack-and-slash system. Like many traditional role-playing games, Kingdom Hearts features an experience point system which determines character development. As enemies are defeated, the player gains experience which culminates in a "level-up", where the characters grow stronger and gain access to new abilities. The amount of experience is shared with all party members and each character grows stronger as experience is gained. Music The music for the series has been primarily composed by Yoko Shimomura. Kaoru Wada works as the arranger for orchestral music, including orchestral renditions of the main vocal themes and the ending themes. The orchestral music was performed by the New Japan Philharmonic Orchestra and the Tokyo Philharmonic Orchestra. Soundtracks were released for the first and third installments following the release of their respective games. A compilation soundtrack was later released that included soundtracks for the entire series, including reworked tracks for the re-released Kingdom Hearts Re:Chain of Memories. While the themes for some of the Disney-based worlds are taken directly from their Disney film counterparts, most of them are given entirely original musical scores. In addition to each world having unique background music, each is given its own battle theme rather than having a common theme to cover all fights. Several of the main characters have themes, and the final boss of each game has several themes played in the various phases of those fights. The fights with Sephiroth feature a modified version of Nobuo Uematsu's "One-Winged Angel" from Final Fantasy VII. The main theme songs for the Kingdom Hearts games were written and performed by Japanese pop star, Hikaru Utada. The three main themes are "Hikari", originally from Kingdom Hearts, "Passion", from Kingdom Hearts II, and "Oath" from Kingdom Hearts III. Each song has an English counterpart, "Simple and Clean", "Sanctuary", and "Don't Think Twice" respectively, for the North American and European releases. Utada was the only singer Tetsuya Nomura had in mind for the first Kingdom Hearts theme song. This marked the first time Utada had produced a song for a video game. Both of the first two theme songs reached notable popularity; on weekly Oricon charts, "Hikari" reached No. 1 in 2002 and "Passion" reached No. 4 in 2005. Development History The