What Do You Call a Box With Strings Across It? Half the Instruments in the World

The classification rests on where the strings are attached rather than on how they are played or what they are made of. In this family the strings run between two points on the body itself, with no neck projecting from it and no separate string carrier, which distinguishes them from lutes, where strings run along a neck, and from harps, where the strings meet the soundboard at an angle rather than running parallel to it. That definition is broad enough to cover instruments that look nothing like each other and narrow enough to be precise, which is what a classification is for.

Members are found across most of the world and are played in every possible way:

• •Struck with hammers, including the piano and the hammered dulcimer
• •Plucked with fingers or picks, including the Japanese koto
• •Bowed, in several central European folk instruments
• •Plucked mechanically, including the harpsichord
• •Simple tube and raft forms across Africa and southeast Asia
• •Ground versions with a pit for resonance, in parts of Africa

Classifying a piano as a member of this family surprises people and follows directly from the definition. Its strings run between two points on a frame that is part of the body, with no neck, so it sits in the same category as a Chinese qin or a Persian santur despite the enormous difference in mechanism and sound. The system that produces that result was devised by Erich von Hornbostel and Curt Sachs in 1914 and classifies instruments by how they produce sound rather than by material, culture or appearance, which avoids the European bias of dividing the world's instruments into strings, wind, brass and percussion.

Placing this family among the others makes the classification usable. Instruments whose sound comes from a vibrating string are divided by how the strings are carried, giving this family plus lutes with a neck, harps with strings at an angle to the soundboard, and a rarer type where strings run between two arms joined by a crossbar. Alongside that sit instruments where a vibrating column of air makes the sound, instruments where the body of the object itself vibrates, and instruments where a stretched membrane does. Electronic instruments were added as a fifth category later, which the original scheme had no reason to anticipate.

An instrument with one string or course per note and no means of stopping them has a specific difficulty that shapes how it is played. It can only produce the notes it is tuned to, so playing in a different key requires retuning, which on an instrument with dozens of strings takes time. Several traditions solve it with movable bridges under each string that can be slid to change the pitch between pieces, which the Japanese koto and the Chinese guzheng both use. Others add levers or a mechanism. And the Western keyboard members solved it by adopting a compromise tuning that is slightly wrong in every key and unusable in none.

Strings running between two points on the body itself, with no neck, define the family, which is why the piano, the harpsichord, the koto and a tube of bamboo with fibres lifted from its own skin all belong to it. The classification sorts by how sound is produced rather than by appearance or culture. Having one string per note means retuning to change key, which movable bridges address.