"Once Upon a Time" is approximately twenty-one seconds long in both Kingdom Hearts and the HD remake. It has a time signature of 4/4. The tempo starts at 87 beats per minute, but slows down throughout the piece [molto rallentando]. The only instrument used is a music box, which is suitable to the sweet, gentle, fairy-tale ending it is intended to reflect. The piece starts at a moderately soft [mezzo piano] dynamic, and gradually decrescendos into nothingness.
