Struck idiophones is one of the categories of idiophones (that is, any musical instrument that creates sound primarily by the instrument as a whole vibrating—without the use of strings or membranes) that are found in the Hornbostel-Sachs system of musical instrument classification.
Struck idiophones are categorised as 11 in the Hornbostel-Sachs system. There are two main categories of struck idiophones, directly (111) and indirectly (112) struck.
A bell /ˈbɛl/ () is a directly struck idiophone percussion instrument. Most bells have the shape of a hollow cup that when struck vibrates in a single strong strike tone, with its sides forming an efficient resonator. The strike may be made by an internal "clapper" or "uvula", an external hammer, or—in small bells—by a small loose sphere enclosed within the body of the bell (jingle bell).
Bells are usually cast from bell metal (a type of bronze) for its resonant properties, but can also be made from other hard materials. This depends on the function. Some small bells such as ornamental bells or cowbells can be made from cast or pressed metal, glass or ceramic, but large bells such as a church, clock and tower bells are normally cast from bell metal.
An idiophone is any musical instrument that creates sound primarily by the vibration of the instrument itself, without the use of air flow (as with aerophones), strings (chordophones), membranes (membranophones) or electricity (electrophones). It is the first of the four main divisions in the original Hornbostel–Sachs system of musical instrument classification (see List of idiophones by Hornbostel–Sachs number). The early classification of Victor-Charles Mahillon called this group of instruments autophones. The most common are struck idiophones, or concussion idiophones, which are made to vibrate by being struck, either directly with a stick or hand (like the wood block, singing bowl, steel tongue drum, handpan, triangle or marimba) or indirectly, with scraping or shaking motions (like maracas or flexatone). Various types of bells fall into both categories. A common plucked idiophone is the Jew's harp.
According to Sachs, idiophones