You have to blow into it like a gazoo.if you can growl and blow at the same time. you'll get it.try a growl blow,three times fast you'll see what I mean.it is really,really hard to learn, but practice makes perfect. blo hard and,blo alot.
you have to make yer throat rumble when blowing,that will give you the deep yer lookin fer!almost makes your throat hurt like a little.it made me horse with kinda of a sore throat.but now i do it, no problem.that is about the best i can describe what I do to get a deep tone.
Pls practice at home and get it down ! before going out in the field and screwing up other hunters ,while yer triing to learn!