A bridge is a device that supports the strings on a stringed musical instrument and transmits the vibration of those strings to another structural component of the instrument—typically a soundboard, such as the top of a guitar or violin—which transfers the sound to the surrounding air. Depending on the instrument, the bridge may be made of carved wood (violin family instruments, acoustic guitars and some jazz guitars), metal (electric guitars such as the Fender Telecaster) or other materials. The bridge supports the strings and holds them over the body of the instrument under tension. Most stringed instruments produce sound through the application of energy to the strings, which sets them into vibratory motion, creating musical sounds. The strings alone, however, produce only a faint sound because they displace only a small volume of air as they vibrate. Consequently, the sound of the strings alone requires impedance matching to the surrounding air by transmitting their vibrations to a larger surface area that displaces a larger volume of air (and thus produces louder sounds). This calls for an arrangement that lets the strings vibrate freely, but also conducts those vibrations efficiently to the larger surface. A bridge is the customary means for accomplishing this. The bridge conducts the vibrations of the strings to a hollowed out chamber in a number of instruments (e.g., violin family, acoustic guitar, balalaika). On electric guitars and electric basses, the bridge conducts the vibrations to the body, but the vibrations of the strings are typically sensed by a magnetic pickup, so that an electric signal is created, which is then connected to a guitar amplifier and a speaker enclosure to produce the sound the performer and audience hears. On electric pianos, the player presses or strikes keys, which cause hammers to strike metal tines. A magnetic pickup senses these vibrations, using the same approach as with an electric guitar (amplifier and speaker).