Crook

(Fr. corps de rechange, ton de rechange; Ger. Stimmbogen).

Detachable lengths of tubing inserted into brass instruments for the purpose of changing the tube length and hence the pitch. Since natural horns and trumpets can sound only the notes of the harmonic series, the sole way of playing this series at another pitch is to alter the fundamental note, and this is done by the crooks, which on the horn used to amount to nine or more, starting from B or C. The earliest mention of a crook is, however, for the trombone, in 1541: it was inserted between slide and bell joints to allow performance of parts lower than those for which the instrument was constructed. Horn and trumpet crooks are of two kinds. The commonest, inserted between mouthpiece and instrument, was known as a ‘terminal’ or ‘mouthpipe’ crook (so called because it incorporates a mouthpipe, which receives the mouthpiece). Less common are ‘medial’ or ‘slide’ crooks, inserted like a tuning-slide and having two legs. In Germany during the 18th century an ‘Inventionshorn’ or trumpet might have had crooks of either kind. The tuning was finely adjusted by inserting short lengths of tubing known as tuning bits next to the crook.

Although the need for crooks was greatly reduced by the invention of valves, many types of instruments were provided with crooks throughout the 19th century – and even into the 20th – so that a given harmonic series could be produced without the use of valves, and in order to preserve the special tonal and technical qualities of crooks.

The term is also applied to the curved metal tube upon which is placed the reed of a bassoon or english horn, and generally to any such removable bent tube holding a mouthpiece, as in saxophones and the deep clarinets.

See also Horn, §2(iii).

ANTHONY C. BAINES/R