Wholelotta,I've said this before but being able to purr on a mouth call came very easy to me.I tongue flutter and teach those that call with me to do the same.Not to offend anyone here but the most realistic sounding purrs especially when it comes to hard aggressive purring to my ears comes from tongue fluttering imho.I'm definately in agreement with BT here a V-cut type call or a split reed give great tones here. The best way I can explain to do it is place your tongue in the position in your mouth like your about to say the letter T.Hold it there and loosen it up bit,now force air through,going over the tip of your tongue.As long as you loosen your tongue up and the air is flowing over the tip of your tongue it should flutter against the roof of your mouth and your top two front teeth.Thats basically it,without a call in youir mouth.Put a call in and go for it.Just like any call you make on a air driven mouth call,air pressure will make a difference in the sound and its imperative that no air escapes to the sides but flows cleanly over the tip of your tongue.With practice it will come and you will be able to regulate the amount of air flow going over your tongue which enable you to produce those soft sweet seductive purrs to those hard aggressive type purrs which in many cases have worked wonders for me on early season flocked up birds!Hope it helps Bob....