An aerodynamic whistle (or call) is a simple aerophone, an instrument which produces sound from a stream of gas, most commonly air. It may be mouth-operated, or powered by air pressure, steam, or other means. Whistles vary in size from a small slide whistle or nose flute type to a large multi-piped church organ.Whistles have been around since early humans first carved out a gourd or branch and found they could make sound with it. Many present day musical instruments are inheritors.