Whistles are available in the keys of D, C, G and F.
There are no tin whistles in the minor keys.
The sound that comes from the whistle depends on what
kind of tin whistle you bought. There are
lots of makers of whistles
and they all produce their own unique tone.
The low whistles which are a lot more expensive than
the ordinary whistle produce a more sweeter
sound
which is an octave lower than original whistles.
Playing a low whistle in a session is much more desirable
than the standard whistle as you won't
drown other
musician's out when you reach the second octave,
the low whistle stays quieter and much softer.
Tip. As there are no tin whistles in the minor keys and say for example you are
at a session and the others are playing a song/tune in the key of Bm then you can then play you're D whistle as this is the
closest key to the key of Bm.
And if the song is in the key of Am then you should play the C whistle.