Don Gero's Mask
Gathering the Frog Choir
Don Gero's Mask is one of the 24 Masks in Majora's Mask. It can be used to receive a Piece of Heart and was previously worn by a hungry Goron in Mountain Village.
Obtaining Don Gero's Mask
In the Goron Shrine, Link finds multiple torches that aren't lit. Link must light all the braziers on fire in order to turn the chandelier. When that is done, the chandelier begins spinning and the Goron Mask can be used to break the pots in the chandelier. The Rock Sirloin can be found in one of these, which Goron Link must carry to the hungry Goron in the Mountain Village. As thank you, the hungry Goron gives Don Gero's Mask to Link.
After Goht is defeated, the whole Snowhead area will begin turning back to normal. In the lake in Mountain Village, there are some lily pads and a lone Frog. To earn a Piece of Heart, Link must summon the rest of the Frog Choir back to Snowhead by talking to them wearing Don Gero's Mask.