First off there are a lot of hunters who use mouth calls with great success. Many find the problem of carrying a large number of mouth calls and the limited amount of sounds the reason to go with a E Caller.
E callers are expensive but you can have many call sounds on it and use it for coyotes, crows, ducks and geese even.
There are ways to cut the cost of a Fox Pro or other E callers, Make your own.
The guts is the small amp.
I have 50.00 dollars in mine, all the parts except the speaker are Radio Shack which is out of business around here. A friend just built one and got all the parts from Amazon.
Sounds are on my Sansa Clip 2 MP3 player. The sounds were down loaded from Wind river site and varmint al's web site.
I have lost count of all the varmints that have been called to the gun with it.
If you want information on building your own PM me.

Al