The origin of musical instruments is lost in the mists of time. It has been suggested that the strings developed from the twang of a bow string and the wind section seems very likely to have developed from the pan-pipes made with lengths of hollow reeds or from the sounds that can be produced by blowing into an animal horn. We shall be more concerned, however, with the essential features that have to be present in any instrument if a usable musical sound is to be produced.