Telegraphy and photography both started with a union of chemistry and optics. Telegraphy didn’t involve sound until later.
The first photograph was by Niepce in 1826, and exposed a pewter plate coated with tar to light from a pinhole camera. The tar changed color where the light was stronger. (Probably a thermal effect, not a light effect.)
The first telegraph used electrolysis, and showed each letter with bubbles from its individual wire. Morse, a painter, started out with a visual telegraph using a pen moving on paper. After his system was tried for a while, the operators realized they were understanding the clicks of the pen without looking at the paper. Soon the pen disappeared and the sound was emphasized.
Polistra's Mill 