Goddess's Harp

The Harp is the primary musical instrument found within Skyward Sword. Zelda can be seen playing the harp early on in the quest, but Link acquires the harp himself after a scene at the Temple of Time. It's probably the same harp that's used by Sheik in OoT.

You can play five songs with the harp. The five songs is: Song of the Goddess, Faraoe's Courage, Nayru's Wisdom, Din's Power and Song of the Hero. All of these songs (except Song of the Goddess) open up ways to the Silent Realm. To get Song of the Hero you have to go to the three dragons: Faron, Eldin and Lanayru. Something that's new for Skyward Sword is that you only can play the songs in some places, not everywhere like with the Ocarina.

When you see a group of Blessed Butterflies it often means that you should play the Goddess's Harp. You do not need to play a ceartain melody, it's just freestyling. There are three things that could happen if you do so. First: Nothing happens. Second: A Sheikah Stone pops up and gives you a treasure and a hint. Third: A wall nearby becomes a Godess Wall.