There are several families of instrument: Chordophones, where the sound is generated by a vibrating string eg. a violin, piano or guitar. Membranophones, where the sound is generated by a vibrating skin eg. a drum. Aerophones, where an oscillating air column is used to produce a tone eg. a flute or organ. Idiophones, where the actual body of the instrument provides the tone eg. a xylophone or castanets. Electrophones, where electric circuits male or amplify a tone eg. an electronic keyboard or theremin.