A chordophone is a musical instrument that makes sound by way of a vibrating string or strings stretched between two points. It is one of the four main divisions of instruments in the original Hornbostel-Sachs scheme of musical instrument classification. Electric string instruments often have an electromagnetic pickup that produces a signal that can be amplified. The electric guitar is the most common example, but many other chordophones use pickups—including mandolins, violins, and the overtone koto.