There's a popular story that Tchaikovsky was inspired to write the pas de deux in The Nutcracker after his sister passed away.
To be clear, I don't know if the story is true - I'm inclined to think the story isn't true - but listening to the pas de deux you absolutely believe it's true. Out of the whole ballet, it's the one piece of music that sounds dramatic and aching and rich with emotionality. It sounds wistful. It sounds like holding on to the edge of a dream with an iron grip because at any moment it might evaporate.
And because it has this emotional complexity to it, I've seen it used so many different ways in adaptations. The 1973 Soviet animated adaptation, instead of the climax of the story, uses it during the flashback of the prince's transformation into the nutcracker, and it works. It works so goddamn well. The pas de deux suddenly turns from a beautiful thing into something tragic, and you can believe that it could only have been written by a man wracked with grief.
I don't know if the story is true. I don't think the story is true. But I can believe it. My god can I believe it.
