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. A number of idiophones that are normally struck, such as vibraphone bars and cymbals, can also be bowed.