Place Medli in the center of the ray of light and kill all of the red and green chus. Go back to Medli and walk around her in circles until all of the purple chus have turned to stone.
While holding Medli, jump off the ledge on the left of the entrance door into the statue room. Fly with Medli until you are just in front of the switch, let go of Medli, and use the skull hammer to skip the fog.
Normally when you must aim a beam of light at a statue, chest, etc., you must be able to hold the light at the target for a while in order to ensure that the object is melted, or the switch is activated. An easy way to do this is to pull out your sword and stand in the beam of light. While shield go into first person perspective, C-up, and you can then aim the light much easier.
In the room with the two switches and the staircase, pickup Medli and head over up onto the second platform on the right. Angle yourself towards the ledge. Jump off and fly about halfway with Medli, then drop her and glide the rest of the way to the ledge with the deku leaf and grab it. From here, use the Command Melody and fly Medli up to you.
Place Medli on the back switch, then jump onto the front switch to lower the staircase. Immediately after the cutscene, sidehop to the right continuously, until you land on the first step of the raising stairs. From here, use the Command Melody to fly Medli over to you.
Similarly to Method 1, pickup Medli and head over to the same ledge on the right and angle yourself with the top of the staircase ledge. Throw Medli, and if you aligned yourself properly, she should land on top of the staircase. Now angle yourself towards the staircase again and pull out a bomb. As the flashing speed increases, jump off of the ledge and pull out the deku leaf to damage boost to the ledge. Unlike Methods 1 and 2 you don't need to use the Command Melody in this method.
In the room with the blocks and the floor master, push the first block into the indention on the floor to open the skylight. Pickup Medli and align facing the breakable wall, between it and the spot of light. Now place Medli and 'call' her. Walk away from the wall and the light will reflect off Medli's harp and reveal the block.
Backup towards the ledge, so that your back is facing the sarcophagus. Backflip towards the sarcophagus, and pull out the deku leaf to glide back to the higher platform. This should have disturbed the sarcophagus and revealed the key. Simply use the boomerang to bring the key to you.
Jump off the ledge and glide to the top of the coffin with the key. You will want to make sure to glide at it from a far enough distance away so that the coffin begins to rattle before you land on top (otherwise it will knock you off). Now glide back to the ledge and boomerang the key.
Climb on top of one of the stalfo's coffins (either one will work), then use leaf pumping to glide over to and grab the mirror shield ledge. Once you've gotten the mirror shield, the same hole will open in the ceiling as would normally happen if you defeated the stalfos, and you can shine light onto the symbol above the door to leave the room.
In the room before the that of the mini-boss, there is a wall on the left of the room (by the latter) that can be broken by shining light on it. However it can be broken without having to call Medli over and reflect light from her harp. Stand in the column of light as close as you can to the ledge while still being in the light. Reflect the light with your shield and while still holding R go into C-up. Now just look down to break the wall.
This trick is especially useful to get back to the statue room quickly and setting up for the following trick.
On the upper ledge in the statue room, place Medli near the wall and the ledge. Backflip, and use the deku leaf to ledge clip OoB. Pull yourself back up onto the ledge and now pickup Medli. From here, you can sidehop behind the statue and proceed.
In the room before the coffin room where you have to play the Earth God's Lyric, angle yourself so that you're facing the statue and backup a bit. Throw Medli and she should land in the light at the proper angle so that the light will reflect off her harp. Now quickly use the mirror shield to bounce the light onto the statue.
Once you enter the mirror room, head over to the right ledge. Using either Medli or a bomb, ledge clip OoB. Just as you clip OoB, hold L and turn Link so that he is facing away from the ledge he used to clip. Now use leaf pumping to get underneath the ground by the far door. If you continue holding L while leaf pumping, you'll have a much easier camera angle to deal with. Once you get back in bounds by the door, side walk, keeping close to the wall in front of you (you want to be careful not to clip too far into the barriers behind you. Now open the door and proceed.
Call tingle and deminish your health to 1/2 heart. Ledge clip using Medli or a bomb and deku leaf above the bottom door. Fall and align yourself at a slight angle so that when you die by bomb you don't get pushed in bounds. Zombie hover and use a red Ting to heal yourself once you are above the level of the loading zone. Just before Tingle heals you, switch from mashing B to the Deku Leaf and glide to the loading zone.
After preforming the ledge clip as in the previous method, there are multiple ways to reach the boss loading zone. Depending on your confidence with leaf pumping, you may choose to either go straight for the loading zone, or use an OoB patch of ground near the boss door and make your way to the loading zone from there.
1) If you are planning to glide directly to the loading zone there are two typical variations you can choose from:
*Use leaf pumping to get under the loading zone and then use a jumpslash to reach it. This requires near perfect leaf pumping, as well as the double magic meter, as if you lose any height while gliding over you probably won't make it.
Like the previous option, use leaf pumping to get under the loading zone, except this time, use a Tingle Bomb just as you get under the loading zone to boost you in. The height requirement on this is slightly more forgiving, but still quite strict on leaf pumping.
2) If you are planning Not to glide directly to the loading zone there is a small patch of OoB ground at the base of the stairs leading to the boss door. Note: both of these methods do not require the double magic meter. Depending on whether or not you have access to the Tingle Tuner you can:
Leaf pump to the small patch of ground, queue a Tingle Balloon, and then run under the loading zone and use a jumpslash to reach it.
*Leaf pump to the small patch of ground, throw a bomb towards the door so that it lands in bounds, and use the deku leaf to blow it closer to the boss door. Then glide under the loading zone and let the bomb explosion boost you into the loading zone.
*Leaf pump to the small patch of ground and walk towards the in bounds region so you are partway in the wall. Play the Command Melody and fly Medli over to you. Pick her up while still OoB and position yourself so the tips of Link's feet are just touching the edge of the invisible ledge (you can use the camera and Link's shadow to find this edge). Now try to make sure you do a small jump off the ground towards the loading zone. If the angle is correct and the jump is small enough Medli will fly you right under the loading zone. Now, to get in, take out your leaf and you will be pulled into the loading zone.
*These methods do not require the Tingle Tuner.
Note: If you have access to the Tingle Tuner, you can use green Tings to refill your magic meter so that you do not need the double magic meter.