The earliest musical instruments were most probably those of percussion. Music consists of two parts: rhythm and tone. To produce a tone requires a certain amount of constructive ingenuity; to obtain a variety of tones from one instrument requires considerably more; whereas rhythm may be produced by beating together any solid substances, or even by clapping the hands. By degrees, various as well as improved qualities of rhythmical sound would be discovered; and the stretching of skins over hoops or hollow vessels would soon suggest itself. In the latter case, especially, a musical tone or note would be the result.