A keyboard instrument is a musical instrument played using a keyboard. The most common of these is the piano. Some other types of keyboard instruments include celestas, which are struck idiophones operated by a keyboard, carillons, which are usually housed in bell towers or belfries of churches or other municipal buildings, and other non-acoustic instruments, such as various electronic organs, synthesizers, and keyboards designed to imitate other musical sounds. Today, the term "keyboard" is most commonly used to refer to keyboard-style synthesizers. Under the fingers of a sensitive performer, the keyboard may also be used to control dynamics, phrasing, shading, articulation, and other elements of expression, depending on the design and inherent capabilities of the instrument.