Instructions
To use the ivory horn, first reach the Witch's Castle. It will not be activated before then.
In the first area, go toward the statues and press the normal attack button to liberate them. Move Susan to the magical note to activate the horn.
Press the following buttons: "Circle, Circle, Triangle, Triangle, X." This will summon Aslan, who will breathe life into a statue. The ivory horn is only activated when standing on musical notes throughout the level, and only by pressing the corresponding buttons.