What does this mean in practical terms?

Would you use the word "acquire" if a company planned to perform a ballet only for one season?

Who is the copyright owner of a ballet? For example if a company brings in a choreographer to create a new ballet, in general is the copyright for that ballet owned by the company?

depends, i guess, on how the contract was written when they created it.

if you were to acquire 'etudes', the ballet belongs to lise lander (or it did if she is still with us) as she was harald lander's widow.
but you can't do the ballet without her permission, just as you couldn't do it without his when he was alive.

and i don't know if this applies everywhere but i've seen a contract for that particular ballet that was a license to do it for a period of 3 years. the company wouldn't necessarily be obligated to do it every year but they would have the right for that long.

i think it just all depends, i don't think there's a set rule of thumb.