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 opening. Unlike typical, single-tone whistles, the shepherd's whistle can emit a range of tones, by using the tongue and mouth to change the shape and size of the "sound box". By moving the tongue and mouth, the resonance, and therefore the sound, can be varied. Shepherd's whistle A shepherd's whistle is a specialized, modulatable, variable-pitch whistle used to train and transmit commands to a sheepdog to aid in herding. Unlike other whistles, they are placed inside the mouth and the sound is controlled by the placement of the tongue. Like tin whistles, while simple, they can be used as musical