A harpsichord is a stringed keyboard instrument in which pressing a key causes one or more strings to be plucked by a small plectrum made of quill or plastic. The strings are held under tension on a soundboard, which is mounted in a wooden case and which amplifies their vibrations. Some harpsichords have multiple keyboards and even a pedalboard, similar to pipe organs. Moreover, some also have stop buttons, which add or remove octaves, and a 'lute stop' button to cause a strip of leather or other material to be pressed against the strings to mute them and simulate the sound of a plucked lute. Used extensively in the Renaissance and Baroque eras, both for accompaniment and for solo performances, harpsichords experienced somewhat of a revival in the twentieth century, mainly for the performance of early music.