Rolmonica player harmonica, circa 1929
These interesting instruments were made in Baltimore in the late 1920's. They employ a modified harmonica in which the instrument plays the same note on the draw as it does on the blow (so that the instrument can be played continuously without pausing to take a breath), and paper rolls with holes are passed over the harmonica holes to determine which notes will be played. These instruments were one of the first commercial applications of bakelite, an early plastic-like material that proved very important as an electrical insulator.