Following after the amazing sounds feautured in KH1, the original soundtrack for KH2 captures the hearts of even those who have not even heard of the game.
Each world, and certain main characters, have their own theme songs. Kairi keeps her original - representing her hopeful, cheery attitude. Riku and Roxas both have more serious, darker themes that portrays their pain, confusion, and struggles amazingly. Sora, being the determined spirit he is, holds a faster, more battle-like, beautifully orchestrated theme that reappears in a section of Kingdom Hearts 2's ending theme, "Fantasia alla marcia", to help add a more plot-focused song to review the events of the game. You might hear familiar tunes in this sequel, for each world's theme has been remixed and changed to fit the mood of the world. Atlantica changed it's theme completely, so that instead of hearing the annoying, elevator-like music of "Under the Sea", Haley Joel Osmont (Sora) and the other stars of this world actually sing along with it. They also sing "Part Of Your World", and two other unique songs ("Swim this way" and "A New Day is Dawning") that were not heard in the movie. Atlantica's new theme, "Isn't it Lovely?", is, in my opinion, beautiful, and a little more soft and gentle, fitting the more serious plot excellently.
The first game of the Kingdom Hearts series had a main theme for the entire game, "Hikari" or "Simple and Clean" which had three versions similar to the sequel, the opening Planitb remix which featured a techno-like, faster version; the orchestrated version, which reappears in KH2; and the ending slower and original version played during the solemn ending. Utada Hikaru proves herself once more with a more matured, darker theme for the top-selling game's sequel. The song, "Passion" or also known as "Sanctuary" to some after watching the MTV preview of the English version(See kh-vids.net), also shares the three versions. The first intro version is also fast-beat and rockier than the ending and the orchestrated. The orchestrated version has about the same stunning quality as "Hikari"'s, making the menu trailer (which appears after leaving the controller alone for a minute or two) a bit more fun and interesting. And last, but certainly not least, the "Passion -After the Battle-" ending theme is a bit more atmospheric, put into more softer, quieter words. Hikaru does an excellent job in proving her emotions, as well as the game's, with her beautiful singing voice. The pianoist, whoever that was, also exceeded the expectations in his/her part. The song, in it's three breathtaking versions, is by far the strongest reason to buy the soundtrack. The other battle music, remixed or original, dramatic songs, and world and character themes complete the discs, yet "Passion" really previews the darker points of the game and puts just about anyone into it's mood.