How to make duck calls?

I do a bit of wood turning and reckon I could have a go at turning duck calls.
My question is, how the heck do you make the quack?

Anyone point me in the right direction?

Buy a cheap old Olt or similar and habe a look inside. The principle is common to all calls. The trick is to get the resonance and harmonics right at varilus volumes. Good luck.

Bloke I know who turns wooden and antler ones gets the reed part from America.

you can make replacement reeds from icecream container plastic and similar..... old credit card/id card plastic is very good.

Good shout. Thanks mate I will give that a go