RE: calling without using calls
I hen purr is a very difficult call to make (correctly) with a diaphram call. I find that I can duplicate it much more easily without a call at all.
The situation you described, of coming suddenly upon some turkeys but having them not spook is not really what I would call a tried and true method, because most of the time they will spook. If you bust them up, in the fall anyway... not sure about the spring, you can often call them back to you. I would suspect you could call a boss gobbler in without the use of a call just as easily as with one. Only handicap is you don't have the volume with your mouth that you do with a call... even a diaphram. But it can most certainly be done.