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
Gaining popularity as a folk instrument in the early 19th century in the Celtic music revivals, penny whistles now play an integral part of several folk traditions. Whistles are a prevalent starting instrument in English traditional music, Scottish traditional music and Irish traditional music, since they are often cheap (under US$10), relatively easy to start with (no tricky embouchure such as found with the flute), and the fingerings are nearly identical to those on the traditional six holed flute (Irish flute, baroque flute). The tin whistle is a good starting instrument to learn the uilleann pipes, which has similar finger technique, range of notes and repertoire. The tin whistle is the most popular instrument in Irish traditional music today.