OK
Take an antler tip dril a 2 -3cm deep hole into it, from the cut not pointy end.
Any diam size hole will do depending on the diam of the antler
1cm in from the end you drilled from, cut vertically down until you just meet the drilled hole.
From the pointed end cut a 45 degree cut down to meet your vertical cut to give you a notch.
Cut a circular section dowel of hardwood the same diam as the drilled hole and at least 2cm long.
Plane off the top 1mm of the dowel and insert it into the drilled hole until it just reaches the notch. Make sure all edges are sharp and free of "burr".
Put whistle on mouth and blow.
No whistle? remove dowel (thats why you make it over long - so you can grip it to pull it out!) and plane a fraction more off the top. You may need to go down to about 2/3 of the original thickness of the wood to get it right.
To tune the whistle - a deeper hole = deeper tone a shallow hole = shriller tone so drill or fill til it sounds right.
Once you are happy glue the dowel into position then shape the mouth piece from the underside to a whistle shape.
I have used this technique with various materials from broom handles to Elder branches, bird bone to antler, with few failures.
I hope you have fun.
