Paul from Dotmatrixsynth makes musical instruments out of printers, here writes – “I’ve got an ongoing project, reprogramming the firmware in these 1985 Epson LQ-500 printers to turn them into musical instruments. I originally just wanted to make a sort of homemade mellotron, but it’s evolved into a much deeper project. These printers (like all printers) have a computer inside that operates all the motors and handles the parallel port, etc. The software that drives that computer is all on an EPROM (a reprogrammable ROM chip.) I remove the EPROM, erase it, and reprogram it with my own software that I’ve developed by reverse engineering the printer and its computer.” Link.