Tin Whistle Fingering Chart
Tin Whistle Fingering Chart for a D Whistle
Key of D
Key of G
Most Irish music are in the keys of D or G. So a "D" whistle is all you really need.
To play a tune in a different key all you need is whistle in that key. The fingering remains exactly the same.
For example Mary Had A Little Lamb is in the key of D and you can play it on "D" whistle. If you play it on a "C" whistle with the exact same fingering it will be in the key of C.