First enter the 2nd part of the Fortress and go into the area where the Greudo Queen is. Don't go near her with the mask, cause she'll see you and say Halt, there is a rat with a funny mask in here. Insted climb on one of the 2 barrels and don't move. Use the hookshot to go ontop of the tank with the zora egg, but not in. From there you can see the Greudo Queen, and also if you look near the vent where your supposed to shoot the bee's nest from, you'll see the bee that signifies the nest, but it'll just be there, suspended in air.
Musical Notes Get the zora mask and go to zora hall.
Put it on and talk to the guy on the stage fidgeting with the speakers. Put the mask on and he'll tell you to play a note. After you play a note, he'll say he needs to turn the sound up. If you go to link, deku, or goron, your notes should be very loud and sound like a guitar. You may need to fidget around with notes to get it to screw the sound up.