who composed the music?
Yoko Shimomura
Kingdom Hearts (video game)
Yoko Shimomura composed and produced the music of "Kingdom Hearts". 
who released kingdom hearts? Square
wiki:19515595
Kingdom Hearts (video game) [SEP] Music
Yoko Shimomura composed and produced the music of "Kingdom Hearts". While there are arranged melodies derived from previous Disney films, most of the soundtrack consists of original themes written specifically for the game by Shimomura. The opening orchestration and ending credits theme were arranged and orchestrated by Kaoru Wada and performed by the New Japan Philharmonic Orchestra. The main vocal theme for the original Japanese release is titled . The English version of "Hikari," "Simple and Clean," was used in the Western releases and the Japanese re-release, "Final Mix". Both versions were composed and performed by Hikaru Utada. Her involvement, along with the Japanese song title, was announced in January 2002.