You and Link just finished to go through the Haunted Wasteland and just arrived in front of the Spirit Temple. Link enters the temple while you go play the Song of storms to fill the little oasis near it and splash some water on your face. You then go back in front of the temple and Link gets out of it a few minutes later. As soon as he gets out, Sheik jumps off the rock he's been standing on, landing right in front of you two to teach you and Link the Requiem of spirits.