Hobbies And Interests
Features
A music box typically has rows of metal reeds of different lengths. A circular cylinder covered with small pins rotates inside the box. The pins are positioned to pluck the reeds as they pass by. Each reed makes a single tone when plucked. As the cylinder rotates, the pins are designed to pluck the reeds in a certain order, creating a tune.
The Reeds
Each reed is a freestanding, springy piece of metal. When a pin pulls back on the reed, it stores energy. As the pin continues to rotate, it releases the reed and that energy causes the reed to spring back. The reed has so much energy stored that it will spring past its resting point, bouncing back and forth for half a second or so. The vibrations are perceived as sound.
Amplification
Music boxes often are mounted on a block of wood to amplify the sound. The reeds are small, so they do not move much air or make much sound. When the music box is mounted on a block of wood, however, the sound is transmitted into the wood. This makes the wood vibrate, too, increasing the vibrating surface area. The wood and reeds can move more air than the reeds alone, so the sound is louder.
Powering the Music Box
All music boxes are operated by gears. In some, a small hand crank is attached to a gear system that turns the cylinder. But many music boxes are powered by a spring. You wind it up, compressing the spring and storing energy. As the spring unwinds, the energy drives the cylinder, playing the music box.
Playing a Tune
The music box cylinder is designed to turn at a constant speed. A single rotation will play an entire melody. Therefore, the distance around the cylinder between two pins determines the amount of time between playing those two notes. For example, if pin B is directly after pin A, it will play in that order. If the distance from pin B to pin C is twice the distance from pin A to pin B, twice as much time will pass between playing B and C than between A and B.