Corrected entry: When first talking to the Happy Mask Salesman, the room is completely empty. After retrieving the Ocarina and returning to the Salesman, he is now sitting in front of a huge organ.
Trivia: When using the bomb mask, anytime it's detonated, Link loses hearts. To prevent this from happening, simply press the defend button to make Link kneel down with his shield covering him, detonate the mask and Link will keep his hearts.
Correction: There is enough time between the events for him to have moved the piano there.
Knever