This morning I stepped out my back door just around daybreak to listen for any birds on the surrounding hills. I gave a very loud crow call and immediately the hills erupted with gobbles. For about 30 seconds there was literally not a second of silence as all the Toms sounded off. I almost had to laugh.
That said, I've had the same response with an owl call, banging something loudly, the dog coming out and barking, etc. I do like a crow call just because it's about the easiest to do loudly and it works.