The mask is given to Link by a hungry Goron in the Mountain Village. To acquire the mask, Link must light all the torches lining the wall of the Goron Shrine, using a Deku Stick and before defeating Goht. Alternatively, Link can light them at once by shooting a Fire Arrow to the torch at the center of the chandelier of hanging pots on the ceiling. Doing either action will cause said chandelier to spin. Goron Link must then roll off of the ramp on the top floor to collide with the pots until some Rock Sirloin falls to the floor. Link must then take the sirloin to the Mountain Village and give it to the Goron standing on a ledge. He will thank Link with Don Gero's Mask.
When worn, the mask allows Link to communicate with frogs around Termina to inform them that the Frog Choir is reuniting to sing again. Although Link can speak to them at any time, the reunion can only take place after Link defeats Goht and spring returns to Snowhead. Reuniting all five frogs to the choir will earn Link a Piece of Heart.
The Goron wearing Don Gero's Mask from Majora's Mask
Goron Link obtaining Don Gero's Mask from from Majora's Mask
Agitha wearing Don Gero's Mask in Hyrule Warriors
↑"You got Don Gero's Mask! It looks just like Don Gero, conductor of the frog choir!" — N/A (Majora's Mask)
↑"Whoa-oh-oh!!! Up here! Up here! I am sorry to bother you from such a high place... But I am very hungry, and I have gotten stuck here. Ooooh...It is so cold... I am so very hungry. I don't think I'm going to make it... I just want to eat once more before I die up here. Something tough and hard to chew... I cannot forget that flavor..." — Goron (Majora's Mask)
↑"Th-That's it! It's so good that I dream about it... Dodongo Cavern's finest quality rock sirloin! This is my absolute favorite! Blessed be this meal! [...] Oh, I almost forgot. Please accept this as a token of gratitude... It was crafted so well that no one would even think twice if you were to direct the frog choir." — Goron (Majora's Mask)
↑"The conducting was spectacular. And all of our members rose to the occasion! This is how deeply we were moved by your spectacular conducting..." — Frog (Majora's Mask)