Use MakeyMakey! Connect arrow keys. Preferably make a guitar interface with earth on the strumming part, and 4 notes on the neck. Here's a youtube vid of me playing it. https://www.youtube.com/watch?v=9LiUle08o1w
I had a bit too much fun enhancing my daughter's stuffed guitar toy with alfoil panels, makey makey and a simple scratch program I made with recordings of my voice played on arrow key inputs. It's only a simple program but was lots of fun.
