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.
Singing bird box
The whistle consists of a miniature organ pipe containing a close-fitting piston which can be moved up and down to give a range of notes of over an octave.