Choir practice

I don't usually sleep through the night, so I have benefited from free concerts at around 4:00 am. That's when the coyotes generally perform. They have a much greater variety of compositions than domestic dogs -- as far as I can tell so far the possibilities are infinite. They do duets as well as solos, and sometimes they do a conversation with others in the distance.

The sounds are often eerie, sometimes rhythmic and sometimes lyric. But why are they doing this? Are they talking with each other, or for some reason announcing themselves? And why in the middle of the night?