But the subtle technique is much, much older than the Fab Four. To find the first fadeout in recorded music, you have to go all the way back to 1918. That's when conductor Gustav Holst recorded an ad hoc fadeout for a piece called 'The Planets.' To capture the vastness of space, he had a choir sing in a separate room and instructed a stagehand to slowly close the door so that their voices would drift off, making listeners feel as though they were drifting far, far away from the known parts of the universe.
For more on the history of fadeouts, check out the above video courtesy of Vox.