Shepherd's whistle
They are also produced commercially. Simple whistles may cost less than 1 USD in bulk; expensive ones may be quite ornate. They are commonly made of plastic, aluminum, stainless steel, silver, brass, titanium, Corian, jade, buffalo horn and other materials.
Tin whistle
The whistle is tuned diatonically, which allows it to be used to easily play music in two major keys a perfect fourth apart and the natural minor key and Dorian mode a major second above the lowest note. The whistle is identified by its lowest note, which is the tonic of the lower of two major keys whose tonics are a perfect fourth apart that the whistle most easily plays in. Note that this method of determining the key of the instrument is different from the method used to determine the key of a chromatic instrument, which is based on the relationship between notes on a score and sounded pitch. Whistles are available in a wide variety of different keys.