If I'm setting up on a field or strutt zone, I mix calls up that I use. Like I've heard mentioned by many other hunters I too call every 15 to 30 min. When I call I use a mouth call and do some soft yelps, just in case there's a bird close. If I hear nothing or it's a little windy or in this years case the woods are really green, I use my glass call or my old lynch box to carry the sound then wait to do it again. I've switched to a mouth call many times just for movement reasons while working a bird. I dont know if it helps me by switching calls but don't think it hurts your chances either. If I know a bird is within 100yds and on his way, I usually don't call, just scratch in the leaves and keep my eyes peeled!