Classical music secrets

Here's one.

Program notes at orchestra concerts often list the entire instrumentation of each piece being played. "Two flutes, one doubling piccolo, two oboes, two clarinets, two bassoons," etc., etc., sometimes at mind-numbing length.

But sometimes what you see on stage doesn't match the printed list. The score calls for three trumpets; on stage, you'll see four. The score lists four horns; five are playing. Why? Because the principal trumpet and principal horn reserve the right not to play all the notes in their parts. Let's say there's a difficult horn solo, and after that an ensemble passage in which all the horns play together. The principal horn might want to rest after the solo. He or she won't play the ensemble passage, and that's why five horns are needed, so all four horn parts are covered when the principal doesn't want to play.

That's accepted orchestral practice, common in the world's top orchestras. I'm not saying there's anything wrong with it. But I doubt you'll ever see any orchestra explain to its audience what's going on -- even though anyone can see more horns on stage than the program notes talk about.