peter fidducia the deer doctor has an excellent DVD called tactics for talking to deer ,and he shows you the proper sounds and where and when to use them.a lot of calls can be made with your mouth,some are better with the gadgets.i enjoyed the tape and lots of useful info,he dont try to sell anything either[;)]
I will second that. Peter Fidducia did the best job I have found of systematizing deer vocalizations and putting them into an understandable framework. I taught both my sons off that DVD.
Has the deer doctor fallen on hard times? I know his book club folded up. He and Kate used to do a bang-up job. I just haven't heard anything from him in a while-- we don't get any of the outdoor channels anymore. KYHillChick swears by Kate's cookbooks. I use her venison sausage recipe.
However, back to the subject. I would go further and say you can make passable copies of all deer vocalizations with a little practice. The problem is the practicality. I still carry a call or two simply because it is easier to pull off a consistent call. Usually around late October I start having sinus trouble. There is nothing worse than trying to call, getting a tickle in your throat, and have that in turn set off a coughing jag.
That's also why I don't do much with bare yelping to turkeys anymore. I still purr and cluck with just my mouth. Yelping really wears out your voice in a hurry.
On the other hand, I would encourage everyone to learn how to do a grunt, bleat, and a snort with just their own voice. It really comes in handy for times when you have a skittish deer that needs to be stopped or called back in. The grunt comes from sucking air back over my chords in reverse to make a croak. I make the bleats and bawls by sticking my tongue behind my back teeth and then rolling the middle up and over and then saying "Maaaa." The sound comes out from either side of my tongue. The snort used to be easy before I grew the beard--much harder now. I put my upper lip over my lower lip and yip. With a little practice you can get the right sound.