Stringed instruments create sound through the vibrations caused by the musician's manipulation of the strings. This is achieved through strumming, striking, plucking or rubbing a bow across the strings. The strings are supported by a bridge that transfers their vibrations into the top of the instrument, referred to as the sound board. The sound board carries the vibrations to the instrument's body, which is called the soundbox or resonator.
The soundbox of the instrument is relied upon to make its vibrations more audible. This is demonstrated with guitars, cellos and pianos through the use of their large, hollow body cavities. The opposite is true of stringed instruments that do not have a soundbox, such as electric guitars. In these cases, the instrument must be plugged in to an electric amplifier for its sound to be heard.
The tightness, weight and length of an instrument's strings affect the sound that it produces. For example, loose and heavy strings vibrate more slowly and create a deeper sound with lower notes. Thin, tight strings result in sounds with a higher pitch. Stringed instruments usually have a combination of thick and thin strings to create different notes. Musicians also control the notes of instruments like guitars and violins by grasping the strings at different points along the bridge. This changes the length of the strings and results in shifts in tone.