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Like any instrument, the guitar produces sound from vibrations. Just like wind instruments vibrate from air blown through them, guitars vibrate because of taught strings that are plucked by the player. The strings transfer vibration to the wood of the instrument, which projects the vibration as sound. The strings are made of metal, usual steel with a small coil of nickel or bronze wrapped rightly around the four bass strings. (There are normally only three wrapped strings on an electric guitar.) The thin strands of metal are stretched tightly across the guitar neck and supported by a piece of bone or plastic on the neck called the nut, and by a bone or metal piece on the body of the guitar called the bridge. These pieces prevent the strings from vibrating except in the distance between the nut and bridge, allowing the strings to be precisely tuned.
When the strings are plucked, they vibrate along their entire length in a certain frequency--the pattern of vibration that produces a musical note. But the sound produced by the strings alone is not loud enough to be heard among other instruments, so the guitar body amplifies the sound. The body of an acoustic guitar is made of up to six pieces of wood that make a box shaped like a gourd. The wood pieces are very thin and usually made of a soft coniferous wood like spruce or cedar, though many employ mahogany and other tropical woods. The thin pieces pick up vibrations very easily, and the box shape lets the wood transfer the vibrations to air inside the guitar, creating sound. The vibrating air is then forced out of a hole in the top of the body, and the sound is amplified outside of the guitar.
Making Musical Notes
The strings are able to be tuned to certain notes because of their limited length, so all that is needed to make different notes is to change the length of vibrating string. The guitar uses frets, thin pieces of metal attached the guitar neck, to limit string vibrations. When a player pushes a string down just behind a fret, the metal stops the string from vibrating behind it, changing the frequency and the musical note produced. Very exact calculations and measurements are needed to arrange the frets, since very slight maladjustment can cause the guitar to play out of tune. When made correctly, however, frets allow any note to be played in any combination.