Beyond the Door is a musical score that is featured in both Kingdom Hearts, Kingdom Hearts Final Mix, Kingdom Hearts Birth by Sleep, and Kingdom Hearts Birth by Sleep Final Mix. It is included in the Kingdom Hearts Original Soundtrack and the Kingdom Hearts Original Soundtrack Complete. Its name refers to what lies beyond the Door to Darkness, Kingdom Hearts. It is played on a pipe organ, and conveys a general theme of awe.
- In Kingdom Hearts, it is played after you defeat the World of Chaos, when Ansem, Seeker of Darkness opens the Door to Darkness leading to Kingdom Hearts. He states that beyond the door lies the power of supreme darkness, but is shocked to find that Kingdom Hearts is filled with light, which destroys him.
- In Kingdom Hearts Birth by Sleep, the score follows each character's final boss level. When the Lingering Will defeats Terra-Xehanort and Kingdom Hearts closes, it can be heard, ending Terra's story. When Ventus defeats Vanitas and destroys the χ-blade in a metaphysical battle at his Station of Awakening, the song can be heard, ending Ventus's story. After Aqua defeats Terra-Xehanort and he sends himself to the Realm of Darkness, "Beyond the Door" plays as Aqua dives in to save him.