It’s very hard to have a completely new idea, even in your dreams.
Long ago I posted about the weird dream I had about a dog instrument (a keyboard connected to dog leashes, with dogs trained to bark at a particular pitch); compare this account of the cat piano from 1650 (via BoingBoing).
One important difference: no animals were harmed in any way in my dream.
Tim Converse 
It’s also very similar to Monty Python’s “Mouse Organ” from the second episode. http://www.ibras.dk/montypython/episode02.htm#5 In that case it’s striking each mouse with a mallet, though.
The Museum of Jurassic Technology has a beautiful Kircher exhibit: http://www.mjt.org/exhibits/Knots.html
They don’t have a cat piano, but they have plenty of other interesting things.
Oops. this link was eaten: http://flickr.com/photos/heathynn/32951592/