I gave it a test run with the Amen breakbeat - it's a law, or an old town charter, or something.
While it was in this state I hooked it up to monomebase and confirmed how the connections line up with a piece of breadboard jumper wire and an LED. It's easy to lose track, so I drew up a little matrix and the connectors on a notepad to make sure I knew for sure what went were.
If you click through to Flickr you can read the annotations for the IN and OUT connectors.
The rainbow wire wasn't strictly necessary, but it does help you keep track of what wire goes were.
I just left the unused wires floating around in case I want to use them later.
Smacbook. I don't want the hassle of tapping the 3.3v from the FTDI chip of my NG edition Arduino, so it will have to wait until I get a current generation Arduino/Freeduino board.
I think the basic idea has got legs though and people could use it to turn a 64 into a virtual 128 or 256 as well.
The LEDs aren't terribly bright, I was probably a bit conservative when I picked the current limiting resistor. You can also pop the tops off and remove the white semi-opaque diffusion 'buttons' for extra brightness. You could also print symbols or legends on a transpant sheet and insert them between the diffusion layer and the red cap to add labels, which is nice. I haven't tried it, but it should work pretty well.