Learn English – What does “much to his chagrin” mean?

Literally it means "A regulation requiring certain or all people to leave the streets or be at home at a prescribed hour" or "the time at which such a restriction begins or is in effect"Merriam-Webster usually because of political instability in a certain country or province. Here, in the context of a concert it means:

Everybody out by 10.00 pm.

That is, the concert is suposed to be over by 10 pm.

Impressor was the word way back when The Royal Navy used the Impress Service to conscript sailors, but this practice died out after the Napoleonic Wars.

[OED] marked Obsolete and rare
Impressor
2. One who impresses or takes by force for the public service.
1781 R. H. LEE in Sparks Corr. Amer. Rev. (1853) III. 409 Let his mill and wagons have protection from the destructive talons of impressors.

If impressor is just too old then what about conscripter?
Not a lot of dictionary activity for that, but that doesn't mean it's 'not a word'.

Here are a few examples of conscripter in print.

For example, citizens who trust the government or a major agent as a protector of legal rights may also trust the government as a fair conscripter for the military.
Trust and Governance by Valerie Braithwaite & Margaret Levi Google Books

Only in Quebec was the navy a major issue, and there the Conservatives and Bourassa's Nationalistes branded it the instrument of Empire and conscripter of young men.
The Sea Is at Our Gates: The History of the Canadian Navy by Tony German (1990) Google Books

She said she had a son that the "conscripters" had tried to get, but that he had got away.
Sketches of War History, 1861-1865: 1896-1903 by The Military Order of the Loyal Legion of the United States Google Books Snippet

...as overseer for the housing provisions for Arabs, and even in some instances as conscripter of local military troops.
Arabica, Volumes 13-14 by Evariste Lévi-Provençal Google Books Snippet

That conscripter can be found among the books digitised in Google Books proves that it's a 'real word', used to mean one who conscripts others and that one can include governments, agencies or individuals.

Conscripter is a very obvious form for a word meaning one who conscripts others. I had rather hoped to find conscriber which isn't quite as obvious but I found nothing, possibly because conscribe is somewhat obsolete these days, compared to conscript.

And should you want to spell it conscriptor, well, you wouldn't be the first.

Shortly afterward, I served as a reluctant draftee in the U.S. army during the Vietnam years.... My father and his father before him cam from a long line of conscript soldiers, regardless of the conscriptor.
The Illumating Icon by Anthony Ugolnik Google Books

As a side note, I'd say conscriptee is unnecessarily 'piratey' as the noun conscript means the same and is much more common.