Carillon strike the inside of the bells, allowing the performer on the bells, or "carillonneur/carillonist" to vary the intensity of the note according to the force applied to the key. Although unusual, real carillons have occasionally been fitted to theatre organs (instead of the metal bars or chimes more often used in simulation), such as the Christie organ installed at the Regal Cinema, Marble Arch, in London. A carillon-like instrument with fewer than 23 bells is called a chime. The carillon is the second heaviest of all extant musical instruments, only ranking behind the largest pipe organs. The heaviest carillon in
A (musical note) the pitch standard. The number designates the frequency in hertz. A lower number equals a lower pitch. By an international treaty signed in 1939, modern pitch is standardized at A-440. However, tuning has varied over time, geographical region, or instrument maker. In 17th-century Europe, tunings ranged from about A-374 to A-403, approximately two to three semitones below A-440. Historical examples exist of instruments, tuning forks, or standards ranging from A-309 to A-455.3, a difference of almost six semitones. Although the official standard today is A-440, some orchestral groups and chamber groups prefer to tune a little higher, at A-442 or