The first button is located in the basement of the Hall of Records which is located
across from the cave.
Go through the door with the spikes and take the elevator down. The button is blue.
The second button is located in the cave where the crazed creature (the Weasel) came out of
when you played the Jack-in-the-Box.
Take the little red car to the center of the spiral. The button is white.
The third button is located in the attic of the little house with the musical pipes. The button is orange.
Note: Press the buttons only once or until you hear the clankety bell sound or else the dead bolt won't open.