We've got two cats. One doesn't seem to mind my guitar at all, the other
can't stand it and belts out of the room as fast as possible when I pick it
up, even before I've started playing. (If she's asleep she wakes up and gets
out).

The funny thing is she doesn't seem to react to a recording of me playing.

I wonder if there are some frequencies which guitars make which don't get
reproduced on stereos but which annoy the hell out of her.

Or maybe she's just a cat with remarkably refined musical taste.