When I go to my grandma's house and my cousin is there, we go out in the horse field. One time when we were out in the field, I heard a little girl singing and swinging, but when I turned in the direction, there was nothing but sound. I asked my cousin if they heard it too or if I was crazy, but they said they had heard it too.
Now every time we go out in the horse field, she is there singing and swinging. Sometimes she even cries out for help, and there will be what sounds like a really bad lighting storm around this "ghost", but it is a perfectly clear day. My theory is that a long time ago, a little girl went outside to swing on her swing set, and started singing, then a horrible lighting storm came out of nowhere and she cried out for help, but got struck by lighting before she could be helped and now she is stuck and swings and sings all day long. Occasionally you can hear the swing creak.
There is another part to this ghost and it is the tug boat ghost. A tug boat crashed in a river the same night the little girl was outside. You can hear the tug boat coming down the river then crashing, but they are not harmful ghosts. You can sometimes hear the tug boat's horn around the time the little girl is crying for help in the storm.