How do antique singing bird music boxes work?

A lifelike bird made of feathers and metal sits at the top of the box. When activated, the bird flaps its wings, turns its head, and opens its beak, as
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A lifelike bird made of feathers and metal sits at the top of the box. When activated, the bird flaps its wings, turns its head, and opens its beak, as chirps and warbles play. Inside the decorative box, there’s a complex system of gears and springs. The chirping sounds are

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