The song of most small birds just sounds like a stream of tweets and whistles to us, but if you slow them down, you can get a wonderful feel for what’s going on.
Here’s a nice compilation of lots of them. I like the little wren at the beginning, the (rather quiet) skylark at about 17:57 has a nice rhythm when slowed down, and the song thrush that follows him is quite fun. If other birds can pick out these details, you can imagine there might be quite a lot of communication going on.
Now, I wonder if you sped up a clip of cows mooing, you could get a similar effect?