I thought it would have something to do with Nick Valentine but it seems to just be random creepy tapes from before the Great War.
Safe bet it has something to do with Lovecraft.
A YouTube video I came across provides an explanation.
https://youtu.be/ddcP44WT93w
But it seems open to interpretation
It's sometimes labeled as a 'quest' in some guides but as far as I know it isn't an actual quest. Finding all of the tapes is just sort of seen as a self-rewarding quest or something like that I suppose.