I would suggest buying a couple sets of plastic crow call mouthpieces, and starting with that. I like the kind with a #2 Morse Taper on them. You can buy this kind of set from several different places, Pioneer turkey calls, Brookside game calls, THO supply etc. That is not the brand I use but it will get you started and makes a pretty good call. You will need to start with a 5/8" bore.
The Morse Taper description refers to the tapered angle (bottom part) of the mouthpieces that gets seated into the barrel. They are #2 size, Morse Taper, so you need a #2 size, Morse Taper
reamer to ream out a small portion of the barrel so they will seat. You can see taper on this pair:
002 by
Lonehowl, on Flickr
Doing this on a drill press is tricky, youll struggle to keep tool/bore straight. I use a metal lathe. I drill a 5/8" hole all the way thru. Actually, I drill an undersized hole and straighten it with a boring bar. This ensures me a good straight bore to work with. I make sure I dont cut over my 5/8 goal. Then a run a 5/8 straight reamer thru the hole to size it, which is important if you will be using a mandrel.
While still on the lathe, I use the Morse Taper #2 reamer and ream the hole to the right depth. I use WD40 on the reamer to do this with. Ive always used WD40 when boring/reaming wood and it works great. Does not hurt the wood one bit. Try it with and without and youll see what I mean.
I take it off the metal lathe and put it onto my wood lathe. I use a tapered mandrel I designed to turn my calls with, inserted into the reamed/tapered part of barrel, but you can simply use a 5/8 mandrel, (I suggest an expanding mandrel) to turn the barrel to shape with, inserted into barrel with the 5/8 bore.. You may or may not enlarge the barrel ID a bit after your done. I do, but you do not have to.
After finishing, seat your mouthpieces and tune.
003 by
Lonehowl, on Flickr
That is all in a nutshell. There are many steps involved, but it can be as simple as you want it to be.
Making wood mouthpieces is a completley different thing. There are a couple different styles you can build, but that is another story...with tears...
004 by
Lonehowl, on Flickr
001 by
Lonehowl, on Flickr
Mark