The world’s only working (modern) Pallophotophone plays 80-year-old NBC radio broadcasts:
The pallophotophone was an early audio recorder created by GE researcher Charles Hoxie in 1922. Rather than using magnetic wire or lacquer disks, the device captured audio waveforms on sprocketless 35 mm film as a series of 12 parallel tracks reflected from a vibrating mirror. It was used to record some of the world’s oldest surviving radio broadcasts on Schenectady, New York radio station WGY between 1929 and 1931.
As a forgotten optical medium, I guess its more modern analog would be laserfilm discs. Sort of working along the right path, but just not practical compared to other media coming out at the time. There’s more about the rediscovered pallphotophone recordings on the GE Reports blog.