Tin whistle all the holes closed, the whistle generates its lowest note, the tonic of a major scale. Successively opening holes from the bottom upward produces the rest of the notes of the scale in sequence: with the lowest hole open it generates the second, with the lowest two holes open, it produces the third and so on. With all six holes open, it produces the seventh. As with a number of woodwind instruments, the tin whistle's second and higher registers are achieved by increasing the air velocity into the ducted flue windway. On a transverse flute this is generally done by
Shepherd's whistle his working dog. They produce clear, high-frequency tones of an easily modulated and variable pitch, allowing the shepherd to communicate a variety of commands. The pitch is at an optimal frequency for the herding dog's hearing, and for penetration and distance to cut through adverse weather when gathering sheep. There are some standard whistle commands, although the commands in use vary. Oral histories have noted primitive whistles made by of folding over a sheet cut from a tin, a jam lid, or dog-food lid, punching a hole, and smoothing sharp edges. They are also produced commercially. Simple whistles may cost