Instruments, mostly with keyboards, that incorporate tuning-forks as the sound source; their descendant the celesta rapidly became a more common alternative. The forks are set in vibration over a resonance chamber and sound a practically pure, and therefore monotonous, tone. The first instrument of this type was Charles Clagget's ‘Aiuton, or Ever-tuned organ’ (1788), in which the forks were bowed by a rotating metal cone. In later instruments the forks are usually struck by hammers. To recreate vowel sounds for acoustic research, Hermann von Helmholtz controlled eight tuning-forks (1856, subsequently 12 forks), tuned to the overtone series of a single note, with an oscillating electromagnetic circuit to produce sustained sounds, using an additional fork to stabilize the circuit.
In 1865 Victor Mustel of Paris introduced the Typophone, which was registered in Great Britain in 1866; Vincent d'Indy included it in Le chant de la cloche (1885) and Henri Duparc in L'invitation au voyage (c1870, later revised for orchestra). In 1872 John Milward extended one of the prongs to produce an octave. After 20 years' work Thomas Machell of Glasgow perfected his ‘dulcitone’ in 1880; it was used in five works by Percy Grainger, including The Warriors (1913–16). Other instruments included the ‘Adiaphon’ of W. Fischer & E.W. Fritzsch of Leipzig (1882) and the ‘Euphonium’ of G.A.I. Appunn of Hanau, a five-octave instrument without resonators (1885).
From 1885, in his Elektrophonisches Klavier, Richard Eisenmann used a system of electromagnets and tuning-fork oscillators to excite and sustain vibrations in piano strings. Helmholtz's use of tuning-forks as a stable vibrating source for controlling an electrical circuit was extended in the Rangertone organ (1931); the forks maintained electro-magnetic tone-wheels at a constant speed, and the tuning of individual notes could be adjusted by changing single forks. The RCA Electronic Music Synthesizer (two models: 1951–2, 1957) included a set of 12 electronically-driven tuning-forks as the primary source of sound. Amplified tuning-forks are featured in the Kamerton pianino (1950s) from the USSR and in several compositions of the 1980s and 90s, including works by Denis Smalley (1985–9), Richard Lerman (1976) and Warren Burt (several works for a specially-built four-octave set of aluminium tuning-forks tuned in 19-note just intonation, with an extended bass range).
H.G. FARMER/HUGH DAVIES