I use a lathe.
You need to decide what you want to get out of callmaking before you start making calls. Do you want to craft a handmade call for specific individuals? Do you want to make your calls out of any number of woods according to an order for one call- a dozen calls? Do you want to flood the market with your "brand" with ads in every sporting magazine available?
Get a feel for what you want to do with your calls before you jump in with both feet. Some folks could care less if their call is one of 10,000 turned to exact dimensions by means of a computer and automated equipment. Other folks like to be able to talk to the callmaker and give specific input or make special requests regarding a sound they want out of their call. I don't see a thing wrong with making calls with a CNC machine... as long as you don't present them as custom made or handmade. There is definitely a market for mass produced calls.