A harpsichord is a keyboard instrument that makes its sound by plucking a set of strings. In a harpsichord, depressing a key raises its back end within the instrument, which in turn lifts one or more jacks, each a thin strip of wood holding a small plectrum made from quill or plastic; each plectrum plucks a single string. The strings are under tension on a soundboard, which is mounted in a wooden case; the soundboard amplifies the vibrations from the strings so that the listeners can hear them. Harpsichord often include more than one choir of strings. Various devices are used to select which choir will sound when playing; these can include simple levers, or in more elaborate instruments the deployment of more than one keyboard.