I use the gargling method, what this means is you push air against your uvula, the thing that dangles in the back of your throat. You keep your tongue in the call just as you normally would, I sometime push the call a bit furthur forward with my tongue but it takes some experimenting. Anyway, you get a nice soft purrrrrrrr and you can change the inflection by changing the amount of air that is coming up from through your throat and also the placement of the call in your mouth, the main thing is learning how to make your uvula jiggle with air. I use a single reed 4 dollar mouth call and it works well, I think because there isn't a large amount of air a double reed or something that takes more air wouldn't work as well, at least it would be more difficult to make it work with this method.