Here we go with a really stupid sample shot. I couldn't even see the subject in the viewfinder. I couldn't see the organ at all until my eyes adjusted to the dark, and then all I could see were the keyboards and the music on the music rack. The camera AF couldn't find the subject, either. I set the 16-50 to AF, focused on the light on the power bar at lower right, just behind the organ, looked up to the left some, and pushed the shutter release.
Beautiful picture? I think not. But I can actually see the subject! The grain (I mean noise) is a bit bigger, but not much, than when I pushed Tri-X 160 to 3200 in the sink after shooting in an amateur level hockey rink in 1963.
So, ISO 51200 isn't really usable, but my good gosh, the K3 actually focused on a pilot light and got a vague image out of the equivalent of a black cat in a coal pit. By the way, the wood of the organ is European Dark Oak with a lacquer finish. Just to make my astonishment even greater, I can detect the colours of the post it notes on the right key cheek.