Music is the only means of understanding among birds and beasts. This may be seen by the gradation of pitch and volume of tone, the manner of tune, the number of repetitions, and the duration of their various sounds. These convey to their fellow-creatures the time for joining the flock, the warning of coming danger, the declaration of war, the feeling of love, and the sense of sympathy, displeasure, passion, anger, fear and jealousy - making a language of itself.