This is a system used to classify all musical instruments. This system was created by Erich Moritz von Hornbostel and Curt Sachs. The Hornbostel-Sachs system is based on how an instrument vibrates to produce sound. Even though the system has been criticized and revised over the years, it is the most widely accepted system of musical instrument classification used by organologists and ethnomusicologists.The system was first published in 1914 with a revised English translation in 1961. Other classification systems date back to the 4th century B.C. The Chinese classified instruments by the material that they were constructed from (stone, wood, silk, etc.). The idea was originally conceived by the Hindus in the 1st century B.C. They created four main groups, vibrating strings, vibrating air columns, percussion instruments made of wood or metal and percussion instruments made with skin heads. Later, the Greeks used a similar system to classify their musical instruments. Organologists such as Martin Agricola then refined the system even further by dividing stringed instruments into the plucked and bowed categories. In the late 19th century, Victor Mahillon, curator of the Brussels Conservatory musical instrument collection, adopted and refined this system. Although his system was limited to the serious instruments of Western music, he used the four groups of strings, winds, drums and other percussion. By expanding on Mahillon's system, Hornbostel-Sachs made it possible to classify any instrument from any culture.The original Hornbostel-Sachs system classified instruments into four main categories. The fifth category is a later revision to include the latest technologies in music performance. Within each category are many subgroups with a formal structure based on the Dewey Decimal classification system. The basic categories of the system are listed below, and a more complete version of the system is found in the appendix ( Table of Musical Instrument Classifications).1 - Idiophones:Instruments which produce sound by vibrating themselves; 2 - Membranophones:Instruments which produce sound by a vibrating membrane; 3 - Chordophones:Instruments which produce sound by vibrating strings;4 - Aerophones:Instruments which produce sound by vibrating columns of air; 5 - Electrophones:Instruments which produce sound electronically.