I know a fair number of comp callers who cannot purr with a diaphram call by vibrating the vocal cords. I've been using a diaphram call my whole life, and I still just purr by rolling my tounge, sans call... tuck it in the cheek. Sounds better that way anyhow... if he is close enough to hear it with a call... he's close enough to hear it without. Best way to make a fighting purr is the motorboat... its a more agressive call anyway.