The meaning of "wound up to the highest pitch"

What is the meaning of "wound up to the highest pitch" in the following sentence:

The people, whose enthusiasm was now wound up to the highest pitch, again made the air resound with their loudest acclamations.

They were as excited as it is possible to be.

You know those clockwork toys that have a sort of handle on their back that you can spin several times, giving mechanical energy to the toy, and then it performs an action? Such as a music box with ballerinas who dance when you spin the handle? That is calling "winding up" the toy. In the context of your phrase it could mean as if the people were figuratively "wound up", that is, they had alot of energy accumulated that they needed to get out of themselves.

"Highest pitch" means a very acute, sharp sound (high on the treble scale). In your sentence it not only gives the idea that they are making noise (later confirmed with "loudest acclamations") but also that again, they are very high on the energetic side of things.

I hope it all makes sense.