An idiophone is any musical instrument that creates sound primarily by the instrument as a whole vibrating—without the use of strings or membranes. It is the first of the four main divisions in the original Hornbostel–Sachs scheme 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.
Most percussion instruments that are not drums are idiophones. Hornbostel–Sachs divides idiophones into four main sub-categories. The first division is the struck idiophones (sometimes called concussion idiophones). This includes most of the non-drum percussion instruments familiar in the West. They include all idiophones made to vibrate by being struck, either directly with a stick or hand (like the wood block, singing bowl, steel tongue drum, triangle or marimba) or indirectly, by way of a scraping or shaking motion (like maracas or flexatone). Various types of bells fall into both categories.
A number of idiophones that are normally struck, such as vibraphone bars and cymbals, can also be bowed.
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