I got hiking a lot at night, and every once in a while I'm stopped dead in my tracks by this noise - sometimes with a little distance you can mistake this for a weird party or kids screaming.
I was out before dawn in South Texas. My father had dropped me off alone to wait for the sunrise. I heard that noise in the distance, coming closer by the minute. There must have been 20 or so. I was scared shitless.
Fee and I were camping a couple months ago and we heard what sounded like two packs of coyotes calling to each other across a big field. It was awesome.