You know how writers always say that something sounds as sweet as a nightingale's song? And how nobody I know, at least, has any notion what that actually means? Well, a whim struck me and I located this nice website full of different birdsongs, including, if you'll scroll down, the nightingale. It is, indeed, a rather pleasant sound (you can hear another bird in the background, but I think it's an owl): a rather liquid, sweet, piercing sound, like copper bubbles breaking in your ears. There you are: now you know!

Lots of other sounds there as well. It's all rather soothing.