Take this all of you non-believers!!! and do it for yourselves, you'll see.
ok, first of all, you need to beat the forest temple so you can travel back and forth in time. as a child, you need to head to lake hylia. when you get there you need to head to the left to the scarecrows, where you need to play an easy-to-remember song for the scarecrow nearest the lake(he's the one that can only remember 8 notes). go back to the scarecrow as an adult, and play that song for him. he'll tell you that his buddy is traveling or whatever, and that he'll tell him to help you whenever he hears that song.
play through the water temple enough to beat dark link, and to get the longshot.
now go to the top of death mountain, drop by and see the fairy so that you have full health and a long timer when you do the next part. go inside the crater. straight across from you is a wooden plank, go across it and from that ledge you can jump down to a small square platform that has a red rupee with either 6 or 8 green rupees around it, anyway that's not important. when you get down there, immediately play the scarecrow's song, he'll appear on an adjacent platform. use the longshot to get over there to him. go across the ledges until you get to the hexagonal platform that you land on whenever you warp. go across the wooden bridge and you will see the cutscene and sheik will teach you the bolero of fire. you can keep going across the bridge and go into darunia's room. you can pull the statue out to go back inside the crater. the door will be open from inside darunia's room, but if you go out into goron city, the door will be shut from the outside.