Author Simon Barnes in his book “The Meaning of Birds” writes about listening to bird song slowed way down. He records the songs, then plays them back at a much slower speed. He wants to hear the individual notes in a song,, the notes humans miss. Whip-poor-will, for example, does not sing the three-note song we hear. Barnes hears five notes. I hear on my recording more than three, at least four, maybe five. The song of a House Wren also is more complex than we hear in the bird's rapid delivery.
I don’t have the required sound equipment for this demo. So, I did it the old-fashioned low-tech way. I played the songs from my bird app on my iPad while recording them in the slow-motion function of my iPhone camera. Try it. It works not well, but well enough. Doesn’t sound at all like bird song, that’s for sure. It's like listening to whales. But the complexity sung by the bird is there.