Edge's Purple Bell
The Harvest Goddess hints that the Purple Bell's pedestal is somewhere high. You know it's not in the lighthouse, so the other high place on Castanet is the Celesta Church.
Go to the church and ask Perry if he's heard of any stories about the church. He says that around 2:00 am at night there is a strange voice that is heard crying somewhere in the building.
Return to the church around 2 o'clock in the morning and you'll bump into Perry as he is running out of the church! Something has scared him off. Check out the door to the right of the alter.
It looks like you've found Edge and the Purple Bell! The strange voice Perry was talking about was Edge's crying. Edge can't ask the bell to ring because the bell's power is run by people's wishes. No one goes to the Wishing Shrine anymore, so the bell won't ring. The Whishing Strine can be found through the door on the left-side of the alter.
The painting on the wall doesn't seem to be anything special. Finn tries to make a wish of his own but the fresco doesn't appear to actually grant any wishes. It's best to ask the Goddess.
The Harvest Goddess says the shrine was a gift to Edge to help him with his loneliness. The bell's spirit is tied to Edge's heart, and so it won't ring if the people don't the shrine their wishes. Since everyone is too busy to go to the shrine themselves, Goddess suggests you talk to everyone in Castanet to hear their wish and then go talk to the Wishing Shrine for them.
In order to hear other people's wishes, you have to raise their friendship up to at least 3 hearts. When you talk to the person he or she will tell you what their wish is.
Once you've heard a wish, return to the Wishing Shrine at the church between 6am and 6pm. Press A in front of the picture and you'll get a list of all the villagers you know. People who have told you their wish will have a red-colored clover next to their names. Select the person, you'll earn a mark on the top-half of the shrine painting, and the clover icon will turn green so you can't select them a second time.
You have to fill in all 10 marks on the wall, so you need to listen to 10 people's wishes.
When you've finished filling in the mural's dots, return to Edge and talk to him. Now he's so happy that he is still crying! Once the Purple Bell rings out, return to the Goddess' Pond.
You can continue to collect wishes from the villagers. Once you have all of the wishes for every character in your game you'll be rewarded with the wish trophy for your house.