Rob, back in the early 80's I watched a booner for 20 minutes from my stand, after rubing several trees, He went back overand stood about 15 to 20 yards inside the edge of the wood line, only raiseing and lowering his head to get a look out into the bean field. When a smaller Buck chased a Doe out of the Corn field into the Bean field, the Booner let out a Loud Aggressive Grunt, (Roar/Growl) and took of at a gate, doing what some call a tending grunt every other step, 5 times!and chased the younger Buck and Doe back into the Corn field. Now Grunt calls came into the picture sometime later, around 84 or 85. Up until that time some of us were doing deer Vocalizations by mouth, I for one was glad because it made my sinus and throat sore, Plus I could not imitate the Roar (not loud or ruff enough) by mouth. After playing with the new grunt calls I could do the loud aggressive grunt by cupping bouth hands over the end of the call, at the beginning of the grunt (lower), and uncupping them at the end of thegrunt (higher with an "erra" on the end). Now Me, and several of my friends and Family have been useing this grunting sequence for at least 20 years. It's not new, just new to some. Hope this helps.