There are 2 ways to purr w/ a diaphram call. One by using your throat which only some people can do. The other is using your lips. I personnaly can't do it with my throat. I never heard of a purr only being good on hens. I like to use a purr when usual yelps, and clucks don't seem to be drawing that tom in. Or when many other hunters have been in the area yelping all over throughout the early morning. I combine a purr with scratching the ground to imitate a feeding hen.