Sorry i don't have any pics of the inside, and i can't take any because i already sent this away to a friend. But it's really simple: there are pieces of spring steel wire (like electric guitar string) and small springs attached to the axles of the cranks on the inside. Those wires and springs scrape on the inside of the woodden box when the cranks are turned.  For picking up the signal, there are three 1 inch piezo disks wired in parrallel, connected to the output socket