When I first started with my current horse, he heard Christmas Carols until he could probably have sung them himself! He was my step-up from a confidence builder that I had needed after a bad wreck. Once the confidence builder became totally boring, I knew it was time for a new horse and a little bit of a challenge. I could handle him, but he was far from the deadbroke almost deadhead I was used to and I think I sang as much to give myself courage as to calm him! LOL I have to admit that it wasn't just singing. I have called him every name in the book and some of them weren't nice at all! I've also reminded him on numerous occasions that dogs have to eat too! LOL
But once we got the hierarchy established (I lead, he follows) I shut up. Now, when I talk to him, his ears swivel back right away and I have his attention. He keeps an ear on me in the round pen... If he heard my voice all the time, I think it would just be background noise to him.