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
Tin whistle "cross-fingering" (covering some holes while leaving some higher ones open). However, half-holing is somewhat more difficult to do correctly, and whistles are available in many keys, so for other keys a whistler will typically use a different whistle instead, reserving half-holing for accidentals. Some whistle designs allow a single fipple, or mouthpiece, to be used on differently keyed bodies. There are larger whistles, which by virtue of being longer and wider produce tones an octave (or in rare cases two octaves) lower. Whistles in this category are likely to be made of metal or plastic tubing, sometimes with a tuning-slide