For those who haven't had any success with a grunt tube, you're doing it wrong. I've had great success with a grunt tube. I use a tru talker, the one that looks like a rubber hose. From October to February I don't go in the woods without it. I do very little blind calling but if I can see him I'm gonna call to him even if I don't plan to kill him. I've found that it works better where it's thick and he can't see good where the call is coming from. The secret is not to call to much. When I see a buck I'll give him a short grunt just loud enough to get his attention. Once I know he heard it I go silent until he starts to move. If he comes my way I don't make a sound. If he continues on the way he was going I'll grunt again until he acknowledges that he heard it then silent again. Think of it like this. You're walking down the street and someone says "Hey". You stop and look where you thought you heard them but you don't see anybody so you continue on. Then you hear it again but don't see anybody. After a few times you'll walk over to where you heard them to try and find whoever it is that keeps calling. It works more times than not.
Example
Sunday afternoon Ashley and I had a 9 point come in behind us and in the process of her trying to turn around and get on him he saw us and spooked. I grunted and he would stop but she couldn't get him in the scope. We did this probably 8 different times until he had circled all the way around and was in front of us before she made the shot. Her best buck so far.
Tuesday morning from the same tree I saw a good buck crossing in front of us and grunted to stop him. Ashley again couldn't get him in the scope. He started to move and I stopped him again, she still couldn't get on him. He stood there probably two minutes and I got impatient and grunted to get him to move. He didn't like it and turned and trotted off.
This morning, Wednesday, I had a four point come in and caught me standing up in the stand to stretch my legs. He bolted and ran about 80 yards and started blowing at me so I grunted in hopes that it would shut him up. It did and three grunts later I had called him back into bow range even though I had no plans of shooting him.