FWIW I found the whole video quite interesting, I had never really considered that there could be sound recordings from before anyone had thought of a way to play them back.
Though I do remember an old mythbusters episode [1] where they tested whether it was possible for audio to be "accidentally" recorded on a pot when a piece of grass happened to mark the pot while spinning.
[1] https://en.wikipedia.org/wiki/MythBusters_(2006_season)#Pott...