This is a cardboard casing synth from FOTOSIS DIY. It's based on the 'Your First Synth' how-to shown here via Music From Outer Space. I think they share my enthusiasm for musical paper. "I think cardboard is a wonderful material to work with and still want to make another more complicated version in cardboard casing. It's cheap, versatile and easy to store or transport. We're big fans of cardboard furniture or anything using recycled materials."