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) A♭ (musical note) A (A-flat; also called la bémol) is the ninth semitone of the solfège. It lies a diatonic semitone above G and a chromatic semitone below A, thus being enharmonic to G, although in some musical tunings, A will have a different sounding pitch than G. When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of the A above middle C (or A) is approximately 415.305 Hz. See pitch (music) for a discussion of historical variations in frequency. A/G is the only note to have only one other enharmonic.