Despite their complaining you must realize you have them in very nice accommodations!! I know this has got to be rough on you, but you are doing the right thing for them, even though it's hard.

At the shelter we will sometimes dim the lights in a room full of caged cats to get them to calm. You could try this and see if it relaxes "singing" Jim at all.

Or perhaps you could give them some "over the counter" kitty drugs--- sprinkle a bit of catnip on one of the shelves?

Stay strong, Jen! You are such a good kitty Mommy!