Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online.A string instrument (or stringed instrument) is a musical instrument that produces sound by means of vibrating strings. In the Hornbostel-Sachs scheme of musical instrument classification, used in organology, they are called chordophones. The most common string instruments in the string family are guitar, violin, viola, cello, double bass, banjo, mandolin, ukulele, and harp. Not often immediately recognized as such, a piano is also a string instrument.