Key (instrument) Key (instrument) A key is a specific part of a musical instrument. The purpose and function of the part in question depends on the instrument. On instruments equipped with tuning machines, violins and guitars, for example, a key is part of a tuning machine. It is a worm gear with a key shaped end used to turn a cog, which, in turn, is attached to a post which winds the string. The key is used to make pitch adjustments to a string. With other instruments, zithers and drums, for example, a key is essentially a small wrench used to turn
Signal instrument Signal instrument A signal instrument is a musical instrument which is not only used for music as such, but also fit to give sound signals as a form of auditive communication, usually in the open air. Signal instruments are often contrasted with melodic and diatonic or chromatic instruments ("a musical (rather than signal) instrument" is not uncommon phrasing). To make the message audible at a distance, percussion and brass instruments, which are generally loud, are chiefly used for this purpose. There are contemporary instruments which evolved from signal instruments, such as the natural horn evolving to the trumpet. Before the